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Background: Joubert syndrome (JBTS) is a heterogenous disorder characterized by intellectual disability, developmental delays, molar tooth sign in brain imaging, hypotonia, ocular motor apraxia and overlapping features of ciliopathies. There are 36 clinical subtypes of JBTS, with an equal number of genes known so far for this phenotype. Methods: Whole exome sequencing (WES) and Sanger sequencing were performed for the molecular diagnosis of a Pakhtun family affected with Joubert syndrome type 9 (JBTS9). Results: A novel homozygous missense variant (c.4417C>G; Pro1473Ala) in exon 34 was identified in coiled‐coil and C2 domains‐containing the protein 2A (CC2D2A; NM_001080522) gene. The variant co‐segregated in autosomal recessive fashion within the family and was not found in 200 ethnically matched unaffected individuals. In silico analyses supported the pathogenic effect of the altered CC2D2A protein. Conclusions: To the best of our knowledge, this is the first report of CC2D2A alteration co‐segragating with a JBTS9 phenotype in a Pakhtun family from Pakistan. Our findings broaden the pathogenic spectrum of JBTS9, adding a novel variant to CC2D2A variation pool. WES analysis is a successful molecular diagnostic tool for rare genetic disorders, especially in those populations where the marriage of cousins is more frequent. Efficient and accurate genetic testing and counselling of the affected families are helpful for patient management and for reducing the disease burden in future generations. [ABSTRACT FROM AUTHOR]

Background: Congenital atrichia (CA) is a rare form of irreversible alopecia with an autosomal recessive mode of inheritance. This form of hair loss is mainly associated with mutations in the human hairless (HR) gene located at chromosome 8p21.3. An additional unique feature atrichia with papular lesions (APL) comprises keratin‐filled cysts known as papules. The present study aimed to uncover the underlying genetic causes of APL in two consanguineous Kashmiri families. Methods: In the present study, two consanguineous families of Kashmiri origin with APL displaying an autosomal recessive mode of inheritance were investigated. Whole exome and Sanger sequencing followed by bioinformatic studies, variant prioritization, Sanger validation and segregation analysis was performed to find the mutation. Results: A recurrent nonsense (NM_005144: c.2818C > T:p.Arg940*) mutation was detected in exon 13 of the human HR gene. Conclusions: Whole exome sequencing analysis has widely been used in the screening of single gene disorders mutations, both in research and diagnostic laboratories. Sanger sequencing alone for genes such as HR becomes expensive and time consuming. Instead, it is recommended that a patient is to screen by whole exome sequencing and then special attention first focuses on known genes of the APL phenotype. This is helpful for intime diagnosis, being more efficient and economic. The results obtained in the present study may contribute to prenatal diagnosis, carrier secreening and the genetic counseling of families with the APL phenotype in Kashmiri poplution. [ABSTRACT FROM AUTHOR]

Background: Syndactyly is a clinical feature of split‐hand foot malformation (SHFM), ectodermal‐dysplasia‐syndactyly (EDSS1) and Cenani–Lenz syndactyly syndromes (CLSS). In EDSS1, only cutaneous syndactyly is observed, with sparse hair, abnormal nails and dentition. In SHFM, bony syndactyly may vary from hypoplasia of one phalanx to aplasia of central digits, extending to complete fusion of all fingers and toes in CLSS. Several genes have been assigned to these syndromes. Performing a single step molecular diagnostics becomes a challenge when a phenotype has overlaps with several syndromes or when some of the clinical features are not fully expressed in patients. Methods: Whole exome sequencing (WES) analysis on one sample derived from a consanguineous family was performed. A causative variant in WES data was prioritized via standard bioinformatics tools. The selected variant was Sanger sequenced in all the available family members for autosomal recessive segregation. Results: A novel missense variant (c.1151A>G; p.Tyr384Cys) was identified in the LRP4 gene. Sanger validation confirmed that all affected individuals were homozygous and the obligate carriers were heterozygous for this variant. The variant is neither reported in 1000 human genomes, nor in 60 706 exomes databases, and is predicted as "pathogenic" by SIFT, Polyphen‐2 and MutationTaster software. Conclusions: The present study broadens the pathogenic spectrum of the LRP4 gene in syndactyly syndromes. WES is a powerful tool for genetic analysis in research and can be readily used as a first‐line diagnostic test in syndactyly and related phenotypes. [ABSTRACT FROM AUTHOR]

Background: Hypohidrotic ectodermal dysplasia (HED) is a rare congenital disorder arising from the abnormal development of ectoderm derived structures, including skin, hair, nails, teeth and glands. These patients have sparse hair on the whole body, including the scalp, as well as hypoplastic teeth. They have no resistance to heat as a result of abnormal sweat glands. In total, four genes, namely ectodysplasin A (EDA), ectodysplasin A receptor (EDAR), EDAR‐associated death domain protein (EDARADD) and Wnt family member 10A (WNT10A), are known to be involved in the etiology of HED. Methods: In the present study, we investigated two consanguineous Kashmiri families (A &B) with an autosomal recessive form of HED. Using whole exome sequencing and different bioinformatics tools, we detected a recurrent mutation causing severe HED. Results: We identified an already known rare homozygous missense (NM_022336 c.1300 T>C; p.W434R; minor allele frequency 0.00007) variant in exon 12 of the EDAR gene. This variant segregated with a homozygous form in all patients and their obligate carriers were heterozygous. A panel of > 100 unrelated ethnically matched controls was screened, and the mutation was not identified outside the families. Furthermore, the candidate variant is predicted to be damaging by in silico software giving a CADD (Combined Annotation Dependent Depletion) score of 25.5, which indicates that the variant is among the top 1% of the deleterious variants in the human genome. Conclusions: The identification of the same homozygous mutation segregating with disease in two different families supports the important role of the gene in the development of the disorder and this may contribute to novel approaches, prenatal diagnosis and genetic counseling of families with EDAR related disorders. [ABSTRACT FROM AUTHOR]

Background: Autosomal recessive cutis laxa type 2A (ARCL2A; OMIM: 219200) is characterized by neurovegetative, developmental and progeroid elastic skin anomalies. It is caused by biallelic variation in ATPase, H + transporting V0 subunit A2 (ATP6V0A2; OMIM: 611716) located on chromosome 12q24.31. Autosomal recessive cutis laxa type 3A (ARCL3A; OMIM: 219150) is another subclinical type characterized by short stature, ophthalmological abnormalities and a progeria-like appearance. The ARCL3A is caused by loss of function alterations in the aldehyde dehydrogenase 18 family member A1 (ALDH18A1; OMIM: 138250) gene located at chromosome 10q24.1., Methods: Whole-exome sequencing (WES), and Sanger sequencing were performed for molecular diagnosis. 3D protein modeling was performed to investigate the deleterious effect of the variant on protein structure., Results: In this study, clinical and molecular diagnosis were performed for two families, ED-01 and DWF-41, which displayed hallmark features of ARCL2A and ARCL3A, respectively. Three affected individuals in the ED-01 family (IV-4, IV-5 and V-3) displayed sagging loose skin, down-slanting palpebral fissures, excessive wrinkles on the abdomen, hands and feet, and prominent veins on the trunk. Meanwhile the affected individuals in the DWF-41 family (V-2 and V-3) had progeroid skin, short stature, dysmorphology, low muscle tone, epilepsy, lordosis, scoliosis, delayed puberty and internal genitalia. WES in the index patient (ED-01: IV-4) identified a novel homozygous deletion (NM_012463.3: c.1977_1980del; p.[Val660LeufsTer23]) in exon 16 of the ATP6V0A2 while in DWF-41 a novel homozygous missense variant (NM_001323413.1:c.1867G>A; p.[Asp623Asn]) in exon 15 of the ALDH18A1 was identified. Sanger validation in all available family members confirmed the autosomal recessive modes of inheritances in each family. Three dimensional in-silico protein modeling suggested deleterious impact of the identified variants. Furthermore, these variants were assigned class 1 or "pathogenic" as per guidelines of American College of Medical Genetics 2015. Screening of ethnically matched healthy controls (n = 200 chromosomes), excluded the presence of these variations in general population., Conclusions: To the best of our knowledge, this is the first report of ATP6V0A2 and ALDH18A1 variations in the Pakhtun ethnicity of Pakistani population. The study confirms that WES can be used as a first-line diagnostic test in patients with cutis laxa, and provides basis for population screening and premarital testing to reduce the diseases burden in future generations., (© 2023 John Wiley & Sons Ltd.)