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In this report, we described a large Han-Chinese family which presents with various phenotypes from unaffected to manifested nystagmus in females. Infantile nystagmus (IN) is characterized by bilateral, involuntary, and periodic eyeball oscillation, occurring at birth or within the first 6 months. The most common inheritance pattern of IN is an X-linked form with incomplete penetrance among females, and the FERM domain containing 7 gene (FRMD7) is a main disease-causing gene. A combination of exome sequencing and Sanger sequencing, as well as detailed clinical examinations were performed on the Chinese IN family. An FRMD7 c.47T>C (p.Phe16Ser) variant was proposed as the disease-causing variant. Incomplete penetrance was found in females with the FRMD7 c.47T>C variant, and hemizygous male affected subjects presented more severe manifestations compared to heterozygous female affected subjects. These findings could enhance genetic counseling and antenatal diagnosis of IN.

Coronavirus disease 2019 (COVID-19) caused by a novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in considerable morbidity and mortality worldwide. COVID-19 incidence, severity, and mortality rates differ greatly between populations, genders, ABO blood groups, human leukocyte antigen (HLA) genotypes, ethnic groups, and geographic backgrounds. This highly heterogeneous SARS-CoV-2 infection is multifactorial. Host genetic factors such as variants in the angiotensin-converting enzyme gene (ACE), the angiotensin-converting enzyme 2 gene (ACE2), the transmembrane protease serine 2 gene (TMPRSS2), along with HLA genotype, and ABO blood group help to explain individual susceptibility, severity, and outcomes of COVID-19. This review is focused on COVID-19 clinical and viral characteristics, pathogenesis, and genetic findings, with particular attention on genetic diversity and variants. The human genetic basis could provide scientific bases for disease prediction and targeted therapy to address the COVID-19 scourge.

Heterotaxy (HTX), a condition characterized by internal organs not being arranged as expected relative to each other and to the left-right axis, is often accompanied with congenital heart disease (CHD). The purpose was to detect the pathogenic variants in a Chinese family with HTX and CHD. A non-consanguineous Han Chinese family with HTX and CHD, and 200 unrelated healthy subjects were enlisted. Exome sequencing and Sanger sequencing were applied to identify the genetic basis of the HTX family. Compound heterozygous variants, c.3426-1G>A and c.4306C>T (p.(Arg1436Trp)), in the dynein axonemal heavy chain 11 gene (DNAH11) were identified in the proband via exome sequencing and further confirmed by Sanger sequencing. Neither c.3426-1G>A nor c.4306C>T variant in the DNAH11 gene was detected in 200 healthy controls. The DNAH11 c.3426-1G>A variant was predicted as altering the acceptor splice site and most likely affecting splicing. The DNAH11 c.4306C>T variant was predicted to be damaging, which may reduce the phenotype severity. The compound heterozygous variants, c.3426-1G>A and c.4306C>T, in the DNAH11 gene might be the pathogenic alterations resulting in HTX and CHD in this family. These findings broaden the variant spectrum of the DNAH11 gene and increase knowledge used in genetic counseling for the HTX family.

Background Tuberous sclerosis complex (TSC) is an autosomal dominant disorder with a variety of clinical findings. Variants in the TSC complex subunit 1 gene (TSC1) or the TSC complex subunit 2 gene (TSC2) are responsible for TSC. Methods Physical examinations, computed tomography scans, and light microscopy analyses were performed on the TSC patient from a Han-Chinese pedigree. Whole-exome sequencing combined with Sanger sequencing were performed on the family members. Results The TSC patient showed typical clinical features, including facial angiofibromas, gingival fibromas, a shagreen patch, hypomelanotic macules, ungual fibromas, subependymal nodules, multiple pulmonary cysts, and renal hamartomas. A de novo heterozygous c.5146delG (p.Ala1716Profs*110) variant in the TSC2 gene was identified in the TSC patient of the Han-Chinese family. To our knowledge, this is the first report of the TSC2 c.5146delG variant associated with TSC. Conclusion The study expanding the disease-causing variant spectrum, suggests that whole-exome sequencing combined with Sanger sequencing may be a method for TSC diagnosis and differential diagnosis, and may facilitate the development of genetic counseling and targeted gene therapy for this disease.

Familial amyloid polyneuropathies (FAPs) are life-threatening, autosomal dominant diseases resulting, in most instances, from transthyretin gene (TTR) variants. A small number of TTR variants lead to leptomeningeal amyloidosis (LA), which is a rare FAP subtype with late-onset central nervous system (CNS) impairment symptoms. Previous studies suggest that LA's CNS selectivity was due to complete endoplasmic reticulum-associated degradation of highly destabilized mutants in peripheral tissues. LA's later age at onset (AAO) was due to lower choroid plexus secretory efficacy. This study reports on a family with LA, including six symptomatic and three presymptomatic members. The LA diagnosis was confirmed by leptomeningeal enhancement on contrast MRI, elevated cerebrospinal fluid protein levels, and positive Congo red staining. The predominant symptoms included headaches, dizziness, vomiting, hallucinations, and cognitive impairments which associated with obstructive hydrocephalus. The TTR p.D38G variant with the lowest secretory efficacy was identified as the genetic cause by whole exome sequencing. The family had a statistically significantly earlier mean AAO of 31.3 ± 7.4 (p = 0.001). These uncommon phenotypes indicate unknown factors influencing the progress of CNS impairment via TTR mutants. Medical imaging examinations suggest the potential early diagnosis value of contrast MRI and the importance of ependyma involvement in LA. LA genetic and clinical data were reviewed and summarized. These findings expand the FAPs' phenotypic spectrum and are valuable in FAP diagnosis, treatment, and further research.

GNE myopathy is a rare, recessively inherited, early adult‐onset myopathy, characterized by distal and proximal muscle degeneration which often spares the quadriceps. It is caused by mutations in the UDP‐N‐acetylglucosamine 2‐epimerase/N‐acetylmannosamine kinase gene (GNE). This study aimed to identify the disease‐causing mutation in a three‐generation Han‐Chinese family with members who have been diagnosed with myopathy. A homozygous missense mutation, c.1627G>A (p.V543M) in the GNE gene co‐segregates with the myopathy present in this family. A GNE myopathy diagnosis is evidenced by characteristic clinical manifestations, rimmed vacuoles in muscle biopsies and the presence of biallelic GNE mutations. This finding broadens the GNE gene mutation spectrum and extends the GNE myopathy phenotype spectrum.

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder primarily characterized by multiple cafe-au-lait macules, peripheral neurofibromas, skinfold freckling, and Lisch nodules. The causative genetic factor is the neurofibromin 1 gene (NF1), which encodes a Ras GTPase-activating protein called neurofibromin. NF1 variants may lead to loss of neurofibromin function and activation of downstream cell growth. This study aims to discover the disease-causing variants responsible for NF1 in two Han Chinese families by using exome sequencing combined with Sanger sequencing. A recurrent missense variant c.269T>C (p.Leu90Pro) and a novel nonsense variant c.2993dupA (p.Tyr998*) in the NF1 gene were identified. These variants co-segregated with the disorder in the pedigrees and were absent in the normal controls. The results broaden the NF1 mutation spectrum responsible for NF1. This may be helpful in genetic counseling, clinical management, and gene-targeted therapies for NF1.

Essential tremor (ET) is one of the most common adult-onset movement disorders. ET and Parkinson's disease (PD) overlap clinically and pathologically, which prompted this investigation into the association of PD risk variants in ET patients. This study was designed to explore the role of variants of two PD-related genes LRRK1 and LRRK2 in a Han Chinese ET population.Genetic analysis of LRRK1, rs2924835, and LRRK2, rs34594498, rs34410987, and rs33949390 variants was conducted on 200 Han Chinese patients with ET and 434 ethnically matched normal controls.No statistically significant differences were identified in either genotypic or allelic frequencies of variants between the ET patients and the control cohort (all p 0.05). Haplotype analysis of three LRRK2 variants (rs34594498, rs34410987, and rs33949390) showed no haplotypes displayed an association with ET risk (all p 0.05).The data suggest that LRRK1 variant (rs2924835) and LRRK2 variants (rs34594498, rs34410987, and rs33949390) are not associated with ET in this Han Chinese population.

Tourette syndrome (TS) is a complex neuropsychiatric disorder with chronic motor and vocal tics. Though the etiology is elusive, strong evidence for a genetic contribution to TS has been established. To date, various chromosomal or genetic alterations have been implicated in its pathogenesis. Recently, the deletion in the arylacetamide deacetylase gene (AADAC) was reported to be associated with TS. To investigate the association between the AADAC gene variants and TS, we conducted genetic analysis of the AADAC gene in 200 Han Chinese patients and 300 ethnicity-matched normal controls. Two variants, including a heterozygous splice-site variant, c.361 + 1G > A (rs762169706), and a missense variant, c.744A > T (p.R248S, rs186388618), were identified in two unrelated patients. The c.361 + 1G > A variant, absent in 300 ethnicity-matched controls, led to the deletion of exon 2 in AADAC mRNA, probably associated with development of TS. The c.744A > T variant, predicted to be damaging, was identified in two normal controls. The findings indicate that the AADAC gene c.361 + 1G > A variant may be a potential candidate factor for TS development, though further investigations are warranted.

Background/Aims: Epidermolytic palmoplantar keratoderma (EPPK) is an autosomal dominant genodermatosis. It is characterized by diffuse yellow keratoses on the palmoplantar epidermis, with an erythematous border. The keratin 9 gene (KRT9) and less frequently the keratin 1 gene (KRT1) are responsible for EPPK. This study aims to identify and analyse genetic defects responsible for EPPK in a Han Chinese pedigree. Methods: A four-generation Han Chinese pedigree containing five individuals affected with EPPK was recruited. Exome sequencing, Sanger sequencing, and bioinformatics tools were conducted to identify the mutation in this pedigree. HaCaT cells were transfected with either wild-type or mutated KRT9. Confocal laser immunofluorescence assay, imaging processing, and statistical analysis were performed to evaluate wild-type and mutant KRT9 groups. Results: A novel heterozygous c.1369C>T transition (p.Leu457Phe) in exon 6 of the KRT9 gene was identified in four patients. It co-segregated with the disorder in the family. Functional analysis showed that withdrawal of the filament network from the cell periphery and particle formation were present in about 10% of Leu457Phe-transfected HaCaT cells, while approximately 3% of cells transfected with wild-type KRT9 showed this phenotype. The particles in mutant group were larger than that in wild-type group (P-value < 0.05). Conclusion: The variant may be the disease-causing missense mutation and produce dominant negative effects by interrupting keratin network formation. This study indicates the pathogenic role of the KRT9 gene mutation in this pedigree with EPPK, and may be helpful in genetic counseling, prenatal diagnosis and gene-targeted therapies of EPPK.

Usher syndrome (USH) is an autosomal recessive disorder characterized by sensorineural hearing loss, progressive visual loss and night blindness due to retinitis pigmentosa (RP), with or without vestibular dysfunction. The purpose of this study was to detect the causative gene in a consanguineous Chinese family with USH. A c.3696_3706del (p.R1232Sfs*72) variant in the myosin VIIa gene (MYO7A) was identified in the homozygous state by exome sequencing. The co‑segregation of the MYO7A c.3696_3706del variant with the phenotype of deafness and progressive visual loss in the USH family was confirmed by Sanger sequencing. The variant was absent in 200 healthy controls. Therefore, the c.3696_3706del variant may disrupt the interaction between myosin VIIa and other USH1 proteins, and impair melanosome transport in retinal pigment epithelial cells. Notably, bilateral auditory brainstem responses were absent in two patients of the USH family, while distortion product otoacoustic emissions were elicited in the right ears of the two patients, consistent with clinical diagnosis of unilateral auditory neuropathy spectrum disorder. These data suggested that the homozygous c.3696_3706del variant in the MYO7A gene may be the disease‑causing mutation for the disorder in this family. These findings broaden the phenotype spectrum of the MYO7A gene, and may facilitate understanding of the molecular pathogenesis of the disease, and genetic counseling for the family.

Muscular dystrophy‐dystroglycanopathy (MDDG) is a genetically and clinically heterogeneous group of muscular disorders, characterized by congenital muscular dystrophy or later‐onset limb‐girdle muscular dystrophy accompanied by brain and ocular abnormalities, resulting from aberrant alpha‐dystroglycan glycosylation. Exome sequencing and Sanger sequencing were performed on a six‐generation consanguineous Han Chinese family, members of which had autosomal recessive MDDG. Compound heterozygous mutations, c.1338+1G>A (p.H415Kfs*3) and c.1457G>C (p.W486S, rs746849558), in the protein O‐mannosyltransferase 1 gene (POMT1), were identified as the genetic cause. Patients that exhibited milder MDDG manifested as later‐onset progressive proximal pelvic, shoulder girdle and limb muscle weakness, joint contractures, mental retardation and elevated creatine kinase, without structural brain or ocular abnormalities, were further genetically diagnosed as MDDGC1. The POMT1 gene splice‐site mutation (c.1338+1G>A) which leads to exon 13 skipping and results in a truncated protein may contribute to a severe phenotype, while the allelic missense mutation (p.W486S) may reduce MDDG severity. These findings may expand phenotype and mutation spectrum of the POMT1 gene. Clinical diagnosis supplemented with molecular screening may result in more accurate diagnoses of, prognoses for, and improved genetic counselling for this disease.

Background Ellis‐van Creveld syndrome (EVC), a very rare genetic skeletal dysplasia, is clinically characterized by a tetrad consisting of chondrodystrophy, polydactyly, ectodermal dysplasia, and cardiac anomalies. The aim of this study was to identify the genetic defect for EVC in a five‐generation consanguineous Han‐Chinese pedigree. Methods A five‐generation, 12‐member Han‐Chinese pedigree was enrolled in this study. Exome sequencing was applied in the proband to screen potential genetic variant(s), and then Sanger sequencing was used to identify the variant in family members and 200 unrelated ethnicity‐matched controls. Results A novel homozygous variant, c.2014C>T, p.(Q672*), in the EvC ciliary complex subunit 1 gene (EVC), was detected in the patient, which was cosegregated with the disease in the family and absent in the controls. Conclusion The identified novel homozygous EVC variant, c.2014C>T, p.(Q672*), was responsible for EVC in this Han‐Chinese pedigree. The findings in this study extend the EVC mutation spectrum and may provide new insights into EVC causation and diagnosis with implications for genetic counseling and clinical management.

Kartagener syndrome (KS), a subtype of primary ciliary dyskinesia (PCD), is characterized by bronchiectasis, chronic sinusitis, male infertility and situs inversus. KS is a genetically heterogeneous disease that is inherited in an autosomal recessive form; however, X-linked inheritance has also been reported. As of this writing [late 2020], at least 34 loci, most of which have known genes, have been reported in the literature as associating with KS. In the present study, we identified a frame shift mutation, c.167delG (p.G56Dfs*26), in the coiled-coil domain containing 151 gene (CCDC151) responsible for KS in a Han-Chinese family. To our knowledge, this is the first report of a CCDC151 c.167delG mutation in the KS patient. These findings may expand the CCDC151 mutation spectrum of KS, and contribute to future genetic counseling and gene-targeted therapy for this disease.

Retinitis pigmentosa (RP), the most common type of inherited retinal degeneration causing blindness, initially manifests as severely impaired rod function followed by deteriorating cone function. Mutations in the rhodopsin gene (RHO) are the most common cause of autosomal dominant RP (adRP). The present study aims to identify the disease-causing mutation in a numerous, four-generation Han-Chinese family with adRP detected by whole exome sequencing and Sanger sequencing. Afflicted family members present classic adRP along with heterogeneous clinical phenotypes including differing refractive errors, cataracts, astigmatism and epiretinal membranes. A missense mutation, c.403C>T (p.R135W), in the RHO gene was identified in nine subjects and it co-segregated with family members. The mutation is predicted to be disease-causing and results in rhodopsin protein abnormalities. The present study extends the genotype–phenotype relationship between RHO gene mutations and adRP clinical findings. The results have implications for familial genetic counseling, clinical management and developing RP target gene therapy strategies.

Background:Alport syndrome (AS) is an inherited familial nephropathy, characterized by progressive hematuric nephritis, bilateral sensorineural hypoacusis and ocular abnormalities. X-linked AS (XLAS) is the major AS form and is clinically heterogeneous, and it is associated with defects in the collagen type IV alpha 5 chain gene (COL4A5).Objective:The purpose of this research is to detect the genetic defect responsible for renal disorder in a 3-generation Han-Chinese pedigree.Methods:Detailed family history and clinical data of the family members were collected and recorded. Whole exome sequencing (WES) was applied in the proband to screen potential genetic variants, and then Sanger sequencing was used to verify the variant within the family. Two hundred unrelated ethnically matched normal individuals (male/female: 100/100, age 37.5 ± 5.5 years) without renal disorder were recruited as controls.Results:Three patients (I:1, II:1 and II:2) presented microscopic hematuria and proteinuria, and the patient I:1 developed uremia and end stage renal disease (ESRD) by age 55 and showed sensorineural hearing loss. Patient II:2 developed mild left ear hearing loss. Cataracts were present in patients I:1 and II:1. A COL4A5 gene missense variant, c.2156G>A (p.G719E), located in the Gly-X-Y repeats of exon 28, was identified to co-segregate with the renal disorder in this family. The variant was absent in 200 ethnically matched controls.Conclusion:By conducting WES and Sanger sequencing, a COL4A5 missense variant, c.2156G>A (p.G719E), was identified to co-segregate with the renal disorder, and it is possible that this variant is the genetic cause of the disorder in this family. Our study may extend the mutation spectrum of XLAS and may be useful for genetic counseling of this family. Further functional studies associated with genetic deficiency are warranted in the following research.

Breast cancer (BC) is the most common female cancer found worldwide. It is responsible for 25% of all cancer patients in females. Hereditary BC accounts for about 5–10% of all BC cases. The breast cancer 1 gene (BRCA1) and the breast cancer 2 gene (BRCA2) are the two most-studied BC susceptibility genes. Genetic testing for disease-causing mutations in BRCA1, BRCA2, and other BC susceptibility genes is strongly recommended for members of families having a BC family history. The present study found a heterozygous c.5722_5723del mutation in the BRCA2 exon 11 of a large Han-Chinese BC family using whole exome sequencing and Sanger sequencing. It may cause DNA double-strand breaks repair dysfunction by disturbing homologous recombination, further resulting in BC. The study findings may help supplement and further improve genetic testing strategies and BC risk estimation methodologies in China.

Background Osteogenesis imperfecta (OI), a genetically determined connective tissue disorder, is characterized by increased bone fragility and reduced bone mass. Clinical presentation severity ranges from very mild types with nearly no fractures to intrauterine fractures and perinatal lethality. It can be accompanied by blue sclerae, dentinogenesis imperfecta (DI), hearing loss, muscle weakness, ligament laxity, and skin fragility. This study sought to identify pathogenic gene variants in a four‐generation Han Chinese family with OI type I. Methods In order to unveil the molecular genetic factors underlying the disease phenotype, whole exome sequencing in a member, with OI type I, of a Han Chinese family from Hunan, China was performed. The variant identified by whole exome sequencing was further tested by Sanger sequencing in the family members. Results A heterozygous missense variant (NM_000089.3: c.3197G>T; NP_000080.2: p.Gly1066Val) in the collagen type I alpha 2 chain gene (COL1A2) was identified in four patients. It co‐segregated with the disease in the family. Conclusion The sequence variant may be a disease‐causing factor resulting in abnormal type I procollagen synthesis and leading to OI type I. This finding has significant implications for genetic counseling and clinical monitoring of high‐risk families and may be helpful for understanding pathogenic mechanism of OI and developing therapies.

Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an autosomal-dominant, inherited, systemic, vascular disorder primarily involving the small arteries. It is characterized by migraine, recurrent ischemic strokes, cognitive decline, and dementia. Mutations in the Notch receptor 3 gene (NOTCH3) and the HtrA serine peptidase 1 gene (HTRA1) are 2 genetic causes for CADASIL. The NOTCH3 gene, located on chromosome 19p13.12, is the most common disease-causing gene in CADASIL.To investigate genetic causes in 2 unrelated Han-Chinese patients with presentations strongly suggestive of CADASIL.Exome sequencing was performed on both patients and potential pathogenic mutations were validated by Sanger sequencing.This study reports on 2 unrelated Han-Chinese patients with presentations strongly suggestive of CADASIL, identifying that NOTCH3 mutations were the genetic cause. A common mutation, c.268CT (p.Arg90Cys), and a novel mutation, c.331GT (p.Gly111Cys) in the NOTCH3 gene, were detected and confirmed in the patients, respectively, and were predicted to be deleterious based on bioinformation analyses.We identified 2 NOTCH3 mutations as likely genetic causes for CADASIL in these 2 patients. Our findings broaden the mutational spectrum of the NOTCH3 gene accountable for CADASIL. Clinical manifestations supplemented with molecular genetic analyses are critical for accurate diagnosis, the provision of genetic counseling, and the development of therapies for CADASIL.

Objective Thin basement membrane nephropathy (TBMN), an autosomal dominant inherited condition in general, is characterized clinically by persistent hematuria and pathologically by thinning of glomerular basement membrane. TBMN is occasionally accompanied with proteinuria, hypertension and renal impairment in some cases. The aim of this study is to explore the genetic defect in a Chinese pedigree with familial hematuria. Design and methods A four-generation Chinese Han pedigree with familial hematuria was recruited. Exome sequencing was conducted in the proband diagnosed as TBMN, followed by verification in the proband and other family members with Sanger sequencing. Results A novel missense variant, c.4616C > G (p.S1539C), in the fibronectin 1 gene (FN1), was identified, and it co-segregated with the disease condition in the family. It was not observed in 100 normal controls. Conclusions A missense variant in the FN1 gene is possibly responsible for familial hematuria or TBMN in this family, which may broaden the phenotype and mutation spectrums of the FN1 gene. A male patient in this family progressed to end-stage renal disease requiring kidney transplantation, supporting that familial hematuria or TBMN may not always be as benign as generally thought. The findings may have new implications for clinical monitoring and genetic counseling of the family, and may also help understand the pathogenesis.

Parkinson's disease (PD) is a common age-dependent neurodegenerative movement disorder related to multiple factors, and genetic factors play an important role in the pathogenesis of PD. Variants in the methylenetetrahydrofolate reductase gene (MTHFR), a gene encoding a folate-dependent enzyme that is involved in homocysteine metabolism, have been reported to be associated with PD. To explore the role of the MTHFR gene in the development of PD in Chinese Han population, we analyzed two MTHFR variants (rs1801131 and rs1801133) in a patient cohort consisting of 512 patients with PD from mainland China and a control cohort consisting of 512 age, gender and ethnicity matched normal subjects. Statistically significant differences in genotypic and allelic frequencies were detected in the MTHFR variant rs1801133 (P=0.022 and 0.007, respectively; odds ratio=0.780, 95% confidence interval=0.651-0.934). In addition, the A-T haplotype of rs1801131-rs1801133 showed a protective role against PD development (P=0.007, odds ratio=0.779, 95% confidence interval=0.650-0.933). Our results suggested that the T allele of rs1801133 variant and A-T haplotype of rs1801131-rs1801133 in the MTHFR gene may decrease the risk of developing PD in Chinese Han population from mainland China.

Parkinson's disease (PD, OMIM 168600) is a neurodegenerative disorder featured by degeneration of melanin-positive dopaminergic neurons. Epidemiologic studies have suggested that PD and malignant melanoma (MM) might share common genetic components. Recently, the p.R160W variant in the melanocortin 1 receptor gene (MC1R, OMIM 155555), a risk factor for MM, has been identified to be associated with PD in Spanish population. To explore whether the MC1R variants are associated with sporadic PD in Chinese population, we designed a case-control comparison study and studied three variants, including rs3212366 (p.F196L), rs33932559 (p.I120T) and rs34090186 (p.R67Q), in the MC1R gene in 512 Chinese Han patients with sporadic PD and 512 age, gender and ethnicity matched normal controls. For rs3212366, only the TT genotype was identified in both PD and control cohorts. For variants rs33932559 and rs34090186, we did not identify any statistically significant difference in either genotypic distribution or allelic distribution between the PD cohort and control cohort, and in addition, we did not identify any related haplotype that would either increase the risk for PD or play a protective role against PD. Our data suggest that none of the three variants of the MC1R gene and related haplotypes be associated with sporadic form of PD in Chinese Han population from Mainland China.

Background & objectives: Alport syndrome (AS) is an inherited disorder characterized by glomerulonephritis and end-stage renal disease (ESRD). The aim of this study was to identify the gene responsible for the glomerulopathy in a Chinese family with autosomal dominant AS using exome sequencing. Methods: A 4-generation, 30-member Chinese Han family was enrolled in this study. Exome sequencing was conducted in the proband of the family, and then direct sequencing was performed in family members of the pedigree and 100 normal controls. Results: A novel frameshift mutation, c.3213delA (p.Gly1072GlufsFNx0169), in the collagen type IV alpha-4 gene (COL4A4) was found to be the genetic cause. Neither sensorineural hearing loss nor ocular abnormalities were present in the patients of this family. Other clinical features, such as age of onset, age of ESRD occurring and disease severity, varied among the patients of this family. Interpretation & conclusions: A novel frameshift mutation, c.3213delA (p.Gly1072GlufsFNx0169) in the COL4A4 gene, was identified in the Chinese pedigree with autosomal dominant AS. Our findings may provide new insights into the cause and diagnosis of AS and also have implications for genetic counselling.

Stargardt disease (STGD1, OMIM 248200) is a common hereditary juvenile or early adult onset macular degeneration. It ultimately leads to progressive central vision loss. Here, we sought to identify gene mutations associated with STGD1 in a three-generation Han Chinese pedigree by whole exome sequencing and Sanger sequencing. Two novel potentially pathogenic variants in a compound heterozygous state, c.3607G>T (p.(Gly1203Trp)) and c.6722T>C (p.(Leu2241Pro)), in the ATP binding cassette subfamily A member 4 gene (ABCA4) were identified as contributing to the family’s STGD1 phenotype. These variants may impact the ABCA4 protein structure and reduce the retinal-activated ATPase activity, leading to abnormal all-trans retinal accumulation in photoreceptor outer segments and in retinal pigment epithelium cells. The present study broadens the mutational spectrum of the ABCA4 responsible for STGD1. A combination of whole exome sequencing and Sanger sequencing is likely to be a time-saving and cost-efficient approach to screen pathogenic variants in genetic disorders caused by sizable genes, as well as avoiding misdiagnosis. These results perhaps refine genetic counseling and ABCA4-targetted treatments for families affected by STGD1.

Limb-girdle muscular dystrophies (LGMD) are a highly heterogeneous group of genetic myopathies characterized by progressive proximal pelvic and/or shoulder girdle muscle weakness, with the onset ages ranging from early childhood to late adulthood. The identification of these dystrophies through genetic testing will not only inform long-term prognosis but will also assist in directing care more efficiently, including more frequent cardiorespiratory monitoring and prophylactic treatments. The aim of this study was to identify the responsible gene in a five-generation Chinese Han pedigree with autosomal recessive LGMD. Exome sequencing was conducted and a novel mutation c.107788T>C (p.W35930R) in the titin gene (TTN) was identified. The mutation co-segregated with the disorder in the family and was absent in normal controls. Our discovery broadens the mutation spectrum of the TTN gene associated with LGMD2J.

Parkinson's disease (PD) is the second most common neurodegenerative disorder and has an elusive etiology. It is likely multifactorial, and genetic defects contribute to its pathogenesis. At least 25 genetic loci and 20 monogenic genes have been identified in monogenic PD. Recessive F-box protein 7 gene (FBXO7) mutations reportedly cause hereditary parkinsonism. To explore the roles of four paralogs (FBXO2, FBXO6, FBXO12, and FBXO41) in PD development, their variants (rs9614, rs28924120, rs6442117, and rs61733550, respectively) were analyzed in 502 Han Chinese patients with PD and 556 age, gender, and ethnicity-matched normal participants in mainland China. Statistically significant differences in genotypic and allelic frequencies were detected only in the FBXO2 variant rs9614 (P = 0.001 and 0.023, respectively; odds ratio 0.819, 95% confidence interval 0.690-0.973) between patients and controls. These results suggest that the FBXO2 variant rs9614 C allele may decrease the PD risk in mainland Han Chinese and may be a biomarker for PD.

Parkinson's disease (PD) is the second-most common etiologically complex neurodegenerative disease. Genetic abnormalities are thought to play an important role in the development of PD. Recently, mutations in the resistance to inhibitors of cholinesterase 3 gene (RIC3) have been reported to cause autosomal-dominant PD in Indian population. To determine whether RIC3 gene coding variant(s) are associated with PD in Han Chinese population, the RIC3 gene coding region in 218 mainland Han Chinese patients with PD and the identified variants in 242 normal controls were examined using direct sequencing analysis. Four known single nucleotide variants (c.354C>A, p.L118L, rs10839976; c.389G>A, p.C130Y, rs55990541; c.403C>T, p.P135S, rs73411617; and c.1054G>A, p.D352N, rs11826236) were identified in the RIC3 gene coding region. No significant differences were observed in either genotypic or allelic distributions between the PD patients and the normal controls (all P>0.05) for these four variants. Haplotype analysis showed that the presence of haplotype A-G-C-G (rs10839976-rs55990541-rs73411617-rs11826236) was associated with a 0.764-fold decreased risk (P=0.049, OR=0.764, 95% CI=0.585-0.999) for PD, whereas the presence of haplotype C-A-C-A was associated with a 2.143-fold increased risk (P=0.039, OR=2.143, 95% CI=1.023-4.488) for PD. The findings indicate that four variants: rs10839976, rs55990541, rs73411617 and rs11826236 in the RIC3 gene coding region may play little or no role in the development of PD. Two RIC3 gene haplotypes of four variants: A-G-C-G, and C-A-C-A might relate to either protection against or increased susceptibility to PD in the Han Chinese population, respectively.

Camptodactyly is a digit deformity characterized by permanent flexion contracture of one or both fifth fingers at the proximal interphalangeal joints. Though over 60 distinct types of syndromic camptodactyly have been described, only one disease locus (3q11.2-q13.12) for nonsyndromic camptodactyly has been identified. To identify the genetic defect for camptodactyly in a four-generation Chinese Han family, exome and Sanger sequencings were conducted and a missense variant, c.1016C>T (p.S339L), in the talin 2 gene (TLN2) was identified. The variant co-segregated with disease in the family and was not observed in 12 unaffected family members or 1,000 normal controls, suggesting that p.S339L is a pathogenic mutation. Two asymptomatic carriers in the family indicated incomplete penetrance or more complicated compensated mechanism. Most of p.S339L carriers also have relatively benign cardiac phenotypes. Expression of wild and mutant TLN2 in HEK293 cells suggested the predominant localization in cytoplasm. Our data suggest a potential molecular link between TLN2 and camptodactyly pathogenesis.

Background A clinical overlap between essential tremor (ET) and Parkinson's disease (PD) has prompted investigation whether these disorders share common genetic factors. The paired-like homeodomain transcription factor 3 gene (PITX3) has been shown to play an important role for the differentiation and survival of midbrain dopaminergic neurons in the substantia nigra pars compacta. The preferential degeneration of those dopaminergic neurons is the pathological hallmark in PD. Aims of the study The purpose of this study was to evaluate whether PITX3 variants are related to susceptibility of ET in Chinese Han population. Methods Genetic analysis of two variants rs3758549 and rs4919621 of the PITX3 gene was conducted in 200 Chinese Han patients with ET and 426 controls. Results We did not identify any statistically significant difference in either genotypic or allelic frequencies of variants between the ET patients and control cohort (all P > 0.05). Haplotype analysis of two variants in the PITX3 gene showed no potential association between the haplotypes and risk of ET (all P > 0.05). Conclusions Our data suggest that PITX3 variants rs3758549 and rs4919621 are not associated with ET in Chinese Han population.

Osteopetrosis is a heritable bone condition featuring increased bone density due to defective osteoclastic bone resorption. Exome sequencing and Sanger sequencing were conducted in Han Chinese family members, some of whom had typical osteopetrosis, and a novel missense variant c.2350A>T (p.R784W) in the chloride channel 7 gene (CLCN7) was identified. This variant cosegregated with the disorder in the family but was not observed in 800 controls. The data indicate that exome sequencing is a powerful and effective molecular diagnostic tool for detecting mutations in osteopetrosis, which is a genetically and clinically heterogeneous disorder. This discovery broadens the CLCN7 gene mutation spectrum and has important implications for clinical therapeutic regimen decisions, prognosis evaluations, and antenatal diagnoses.

Autosomal recessive juvenile parkinsonism (AR-JP) is a distinct clinical and neuropathologic entity characterized by early onset parkinsonism and localized neuronal degeneration in the substantia nigra without Lewy bodies. The purpose of this study is to identify the genetic defect in a Chinese pedigree with familial AR-JP and to explore genotype-phenotype correlation. A three-generation Chinese Han pedigree with familial AR-JP was recruited in this study, and the patients in the pedigree presented with typical but heterogeneous clinical features of AR-JP and with different ages of disease onset. Exome sequencing and Sanger sequencing were conducted in the index case diagnosed as juvenile parkinsonism and a homozygous variant, c.850G > C (p.G284R), in the parkin gene was identified. The homozygous variant co-segregated with the disease in the family and was absent in 800 controls. The homozygous variant, c.850G > C (p.G284R), in the parkin gene is possibly responsible for AR-JP in this pedigree. Heterozygous c.850G > C mutation carriers were free of any neurological symptoms, consistent with a loss-of-function mechanism of the parkin mutations. These findings may provide new insights into the cause and diagnosis of AR-JP and have implications for genetic counseling.

Focal segmental glomerulosclerosis (FSGS) is the most common glomerular histological lesion associated with high‐grade proteinuria and end‐stage renal disease. Histologically, FSGS is characterized by focal segmental sclerosis with foot process effacement. The aim of this study was to identify the disease‐causing mutation in a four‐generation Chinese family with FSGS. A novel missense mutation, c.1856G>A (p.Gly619Asp), in the collagen type IV alpha‐4 gene (COL4A4) was identified in six patients and it co‐segregated with the disease in this family. The variant is predicted to be disease‐causing and results in collagen IV abnormalities. Our finding broadens mutation spectrum of the COL4A4 gene and extends the phenotypic spectrum of collagen IV nephropathies. Our study suggests that exome sequencing is a cost‐effective and efficient approach for identification of disease‐causing mutations in phenotypically complex or equivocal disorders. Timely screening for COL4A3/COL4A4 mutations in patients with familial FSGS may help both accurately diagnose and treat these patients.

Background: Congenital cataract is a common cause of childhood vision impairment or blindness with genetic and clinical heterogeneity. The aim of this study was to identify the disease-associated gene in a Chinese family with congenital cataract. Methods: A four-generation Chinese family with three enrolled patients suffering from congenital cataract was studied. Detailed family history and clinical data of all the members were collected and recorded. Exome sequencing was applied in the proband to screen potential genetic variants, and then Sanger sequencing was used to verify the variant within the family. Results: A heterozygous variant, c.3673G > A (p.V1225M), in the periaxin gene ( PRX ) was identified in three patients and two asymptomatic individuals of the family. The variant was absent in the other three unaffected family members and in 3290 ethnically matched in-house controls from BGI-Shenzhen. Conclusions: By utilizing both exome sequencing and Sanger sequencing, we identified a missense variant in the PRX gene that is possibly associated with disease in this family. Our finding may broaden the spectrum of genes associated with congenital cataract, and may provide insights into lens development, pathogenic mechanism, future clinical genetic diagnosis and therapy of congenital cataract.

Essential tremor (ET) is one of the most frequent neurological disorders with elusive etiology, typically characterized by postural and kinetic tremors. Evidence reveals that genetic components are implicated in the development of ET and there are some overlaps between ET and Parkinson’s disease in clinical features and etiology. Variants in the fibroblast growth factor 20 gene (FGF20) have been reported to be associated with the risk of Parkinson’s disease. To evaluate the association between the FGF20 gene variants and ET susceptibility, we conducted genetic analysis of five FGF20 variants (rs1721100, rs1989754, rs10089600, rs12720208, and rs17550360) in 200 patients with ET and 426 ethnically-matched Chinese Han normal controls. Statistical analysis did not identify significant differences in genotypic or allelic frequencies of variants between ET patients and normal controls (all P > 0.05). No related haplotype was found to be related to the risk of ET. The findings indicate the FGF20 gene might not play a dominating role in the genetic predisposition to ET in Chinese Han population.

Oculocutaneous albinism (OCA) is a group of heterogeneous and autosomal recessive disorders characterized by a reduction or complete loss of melanin biosynthesis in melanocytes. OCA type 1 (OCA1) is the most severe and common form of OCA, and is caused by mutations in the tyrosinase gene (TYR). The present study aimed to identify the genetic cause of OCA1 in a four‑generation consanguineous Chinese Han family. Complete physical examinations were performed and blood samples were collected from five members of the family and 100 unrelated healthy controls. Exome sequencing was conducted in the proband, followed by verification in other family members, using Sanger sequencing. Patients in the family presented with typical OCA1 features, including hypopigmentation of the skin and hair, and distinctive ocular changes. A homozygous missense variant, c.896G>A (p.R299H), in the TYR gene was identified in two patients, which co‑segregated with disease in the family. This variant was not present in the 100 healthy controls. These results expand the number of mutations identified to be responsible for OCA1 in the Chinese Han population, and may have implications for genetic counseling and clinical management of the disease.

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease and is characterized by the degeneration of dopaminergic neurons in substantia nigra. Recently, rs75932628 (p.R47H) of the triggering receptor expressed on myeloid cells 2 gene (TREM2) was identified to be associated with PD in American, Spanish, Irish, and Polish population. To explore whether TREM2 variants are related to susceptibility of sporadic PD in Chinese Han population, we designed a case-control comparison study and studied two variants rs75932628 (p.R47H) and rs2234253 (p.T96K) of the TREM2 gene in 512 Chinese Han patients with sporadic PD and 512 age, gender and ethnicity matched normal controls from Mainland China. No variant for either rs75932628 or rs2234253 was found in both PD and control cohorts. Our data suggest that neither variant rs75932628 nor rs2234253 be a major susceptibility factor of sporadic PD in Chinese Han population from Mainland China.

Congenital contractural arachnodactyly (CCA, OMIM 121050), also known as Beals-Hecht syndrome, is an autosomal dominant disorder of connective tissue. CCA is characterized by arachnodactyly, dolichostenomelia, pectus deformities, kyphoscoliosis, congenital contractures and a crumpled appearance of the helix of the ear. The aim of this study is to identify the genetic cause of a 4-generation Chinese family of Tujia ethnicity with congenital contractural arachnodactyly by exome sequencing. The clinical features of patients in this family are consistent with CCA. A novel missense mutation, c.3769T>C (p.C1257R), in the fibrillin 2 gene (FBN2) was identified responsible for the genetic cause of our family with CCA. The p.C1257R mutation occurs in the 19th calcium-binding epidermal growth factor-like (cbEGF) domain. The amino acid residue cysteine in this domain is conserved among different species. Our findings suggest that exome sequencing is a powerful tool to discover mutation(s) in CCA. Our results may also provide new insights into the cause and diagnosis of CCA, and may have implications for genetic counseling and clinical management.

PURPOSE Congenital cataract is a visual impairment that needs correction as early as possible after birth. This study aimed to identify whether genetic defects exist in a Chinese Han pedigree with congenital nuclear cataract. METHODS A family consisting of six members and three patients with nuclear cataract spanning three generations and 100 unrelated ethnically matched normal subjects were recruited in this study. Exome sequencing was performed in the 24-year-old proband, and Sanger sequencing was then conducted in other family members and 100 normal controls. RESULTS A novel missense variant, c.428G>A (p.G143E), in the gap junction protein-alpha 3 gene (GJA3) was identified in three patients of the family but unidentified in three family members without lens opacity and 100 normal controls. CONCLUSIONS A novel missense mutation, c.428G>A (p.G143E), in the GJA3 gene, localized to the cytoplasmic loop, was suggested to be the genetic cause of congenital nuclear cataract, which further expands the gene mutation spectrum. Our findings suggest that exome sequencing is a powerful and cost-effective tool to discover mutation(s) in disorders with high genetic and clinical heterogeneity. Further functional studies in the GJA3 gene mutations may help uncover pathogenic mechanisms of congenital cataract and therefore provide a possible genetic therapy for this disorder.

Polydactyly is one of the most common inherited limb abnormalities, characterised by supernumerary fingers or toes. It results from disturbances in the normal programme of the anterior–posterior axis of the developing limb, with diverse aetiology and variable inter- and intra-familial clinical features. Polydactyly can occur as an isolated disorder (non-syndromic polydactyly) or as a part of an anomaly syndrome (syndromic polydactyly). On the basis of the anatomic location of the duplicated digits, non-syndromic polydactyly is divided into three kinds, including preaxial polydactyly, axial polydactyly and postaxial polydactyly. Non-syndromic polydactyly frequently exhibits an autosomal dominant inheritance with variable penetrance. To date, in human, at least ten loci and four disease-causing genes, including theGLI3gene, theZNF141gene, theMIPOL1gene and thePITX1gene, have been identified. In this paper, we review clinical features of non-syndromic polydactyly and summarise the recent progress in the molecular genetics, including loci and genes that are responsible for the disorder, the signalling pathways that these genetic factors are involved in, as well as animal models of the disorder. These progresses will improve our understanding of the complex disorder and have implications on genetic counselling such as prenatal diagnosis.

Spondyloepiphyseal dysplasia congenita (SEDC) is an autosomal dominant chondrodysplasia characterized by disproportionate short-trunk dwarfism, skeletal and vertebral deformities. Exome sequencing and Sanger sequencing were performed in a Chinese Han family with typical SEDC, and a novel mutation, c.620G>A (p.Gly207Glu), in the collagen type II alpha-1 gene (COL2A1) was identified. The mutation may impair protein stability, and lead to dysfunction of type II collagen. Family-based study suggested that the mutation is a de novo mutation. Our study extends the mutation spectrum of SEDC and confirms genotype-phenotype relationship between mutations at glycine in the triple helix of the alpha-1(II) chains of the COL2A1 and clinical findings of SEDC, which may be helpful in the genetic counseling of patients with SEDC.

Growing evidences show that genetic abnormalities play an important role in the etiopathogenesis of Parkinson disease (PD). At least 18 genetic loci and 13 disease-related genes for parkinsonism have been identified. Recently, the p.Ala502Val and p.Arg1205His variants in the eukaryotic translation initiation factor 4-gamma 1 gene (EIF4G1) were found to be associated with PD. To evaluate whether the EIF4G1 p.Ala502Val and p.Arg1205His variants are related to PD in Chinese Han population, we conducted genetic examination of these two variants in 425 PD patients from Mainland China and none was found in our patients. We did identify a known non-pathogenic polymorphism c.3660C>T (p.Ala1220Ala, rs143852330) in a 73-year-old male patient. Our results, consistent with other recent reports, suggest that the EIF4G1 p.Ala502Val and p.Arg1205His variants are a rare cause of PD, at least in Chinese population.

Febrile seizures (FS), the most frequent type of seizures in children, occur in neurologically normal infants and children between the ages of 3 months and 5 years with genetic predisposition. The aim of this study was to identify the responsible gene in a four-generation Chinese Han pedigree with autosomal dominant FS. Seven family members (three affected and four unaffected) were enrolled in this study. Exome sequencing was conducted and a duplication mutation c.649dupC (p.R217Pfs*8) in the proline-rich transmembrane protein 2 gene (PRRT2) was identified. The mutation co-segregated with the disorder and was absent in normal controls. To our knowledge, this is the first report of a pedigree with complete penetrance of FS, which is caused by mutation in the PRRT2 gene. FS is a novel phenotype of the c.649dupC (p.R217Pfs*8) mutation. Our discovery broadens the spectrum of genetic causes of FS and the spectrum of phenotypes linked to mutation in the PRRT2 gene.

Parkinson disease (PD) is the second most common progressive neurodegenerative disorder. It is characterized by selective loss of dopamine-producing neurons and aggregation of alpha-synuclein (SNCA) in neurons of particular brain regions. At least 20 loci and 15 disease-causing genes have been identified. Rare missense or multiplication mutations in the SNCA gene have been reported to be involved in some familial and sporadic cases of PD. More recently, two novel pathogenic missense mutations (p.H50Q and p.G51D) were identified in the SNCA gene. To evaluate whether mutation(s) in the coding region of SNCA gene is related to PD in Chinese population, we investigated the SNCA gene in 502 PD patients of Chinese Han ethnicity from Mainland China. No pathogenic mutation was identified in the coding region of the gene. A known G to A transition (c.306 + 66G>A, rs10005233) in the intron 4, which does not potentially change splicing, was identified. Our data indicate that mutations in the coding region of the SNCA gene are not likely to be a common cause of PD in Chinese population.

Congenital cataract, a clinically and genetically heterogeneous lens disorder is defined as any opacity of the lens presented from birth and is responsible for approximately 10% of worldwide childhood poor vision or blindness. To identify the genetic defect responsible for congenital nuclear cataract in a four-generation Chinese Han family, exome and direct Sanger sequencings were conducted and a missense variant c.139GA (p.D47N) in the gap junction protein-alpha 3 gene (GJA3) was identified. The variant co-segregated with patients of the family and was not observed in unaffected family members or normal controls. The above findings indicated that the variant was a pathogenic mutation. The mutation p.D47N was found in the first extracellular loop (El) domain of GJA3 protein. Our data suggest that exome sequencing is a powerful tool to discover mutation(s) in cataract, a disorder with high genetic heterogeneity. Our findings may also provide new insights into the cause and diagnosis of congenital nuclear cataract and have implications for genetic counseling.

Familial hypophosphatemic rickets (HR), the most common inherited form of rickets, is a group of inherited renal phosphate wasting disorders characterized by growth retardation, rickets with bone deformities, osteomalacia, poor dental development, and hypophosphatemia. The purpose of this study was to identify the genetic defect responsible for familial HR in a four-generation Chinese Han pedigree by exome sequencing and Sanger sequencing. Clinical features include skeletal deformities, teeth abnormalities, hearing impairments and variable serum phosphate level in patients of this family. A novel deletion mutation, c.1553delT (p.F518Sfs*4), was identified in the X-linked phosphate regulating endopeptidase homolog gene (PHEX). The mutation is predicted to result in prematurely truncated and loss-of-function PHEX protein. Our data suggest that exome sequencing is a powerful tool to discover mutation(s) in HR, a disorder with genetic and clinical heterogeneity. The findings may also provide new insights into the cause and diagnosis of HR, and have implications for genetic counseling and clinical management.

There is growing evidence that genetic abnormalities play an important role in the pathogenesis of Parkinson disease (PD). At least 18 genetic loci and 13 disease-related genes for parkinsonism have been identified. The S100 calcium-binding beta (S100B), which is expressed and secreted by astrocytes, has been found to be associated with PD. To evaluate whether the S100B variants are related to PD in Chinese Han population, we conducted genetic examination of the S100B gene in 502 PD patients from Mainland China. We did identify two known variants c.279+4T>C (rs187503470) and c.99C>G (p.Leu33Leu, rs1051169) in our patients. Neither of these two variants is predicted to change amino acid or splice site, indicating that they are not pathogenic mutations. Our results suggest that mutations in the coding region or intron/exon boundaries of the S100B gene play little or no role in the development of PD in Chinese population.