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ERI1 is a 3-to-5 exoribonuclease involved in RNA metabolic pathways including 5.8S rRNA processing and turnover of histone mRNAs. Its biological and medical significance remain unclear. Here, we uncover a phenotypic dichotomy associated with bi-allelic ERI1 variants by reporting eight affected individuals from seven unrelated families. A severe spondyloepimetaphyseal dysplasia (SEMD) was identified in five affected individuals with missense variants but not in those with bi-allelic null variants, who showed mild intellectual disability and digital anomalies. The ERI1 missense variants cause a loss of the exoribonuclease activity, leading to defective trimming of the 5.8S rRNA 3 end and a decreased degradation of replication-dependent histone mRNAs. Affected-individual-derived induced pluripotent stem cells (iPSCs) showed impaired in vitro chondrogenesis with downregulation of genes regulating skeletal patterning. Our study establishes an entity previously unreported in OMIM and provides a model showing a more severe effect of missense alleles than null alleles within recessive genotypes, suggesting a key role of ERI1-mediated RNA metabolism in human skeletal patterning and chondrogenesis.

Kyphomelic dysplasia is a heterogeneous group of skeletal dysplasias characterized by severe bowing of the limbs associated with other variable findings, such as narrow thorax and abnormal facies. We searched for the genetic etiology of this disorder. Four individuals diagnosed with kyphomelic dysplasia were enrolled. We performed whole‐exome sequencing and evaluated the pathogenicity of the identified variants. All individuals had de novo heterozygous variants in KIF5B encoding kinesin‐1 heavy chain: two with c.272A>G:p.(Lys91Arg), one with c.584C>A:p.(Thr195Lys), and the other with c.701G>T:p.(Gly234Val). All variants involved conserved amino acids in or close to the ATPase activity‐related motifs in the catalytic motor domain of the KIF5B protein. All individuals had sharp angulation of the femora and humeri, distinctive facial features, and neonatal respiratory distress. Short stature was observed in three individuals. Three developed postnatal osteoporosis with subsequent fractures, two showed brachycephaly, and two were diagnosed with optic atrophy. Our findings suggest that heterozygous KIF5B deleterious variants cause a specific form of kyphomelic dysplasia. Furthermore, alterations in kinesins cause various symptoms known as kinesinopathies, and our findings also extend the phenotypic spectrum of kinesinopathies. [ABSTRACT FROM AUTHOR]

We present two unrelated Japanese pedigrees with achondrogenesis type 1b (ACG1B), characterized by prenatally lethal fetal hydrops and severe micromelia. The affected members in these pedigrees carried a common homozygous missense point mutation in solute carrier family 26 member 2 (SLC26A2), a gene associated with ACG1B (NM_000112:c.1987G>A). This loss‐of‐function point mutation causes substitution of glycine 663 with arginine in a highly conserved loop domain of SLC26A2. Interestingly, only a few cases of this mutation have been registered in Japanese genomic databases, and there are no reports of this mutation in any major genomic databases outside Japan. Furthermore, we confirmed the presence of a homozygous stretch of approximately 75 kb surrounding the pathogenic variant. Our findings suggest that this missense point mutation in SLC26A2, which is likely the cause of the ACG1B phenotypes in these unrelated fetuses, is distributed exclusively in Japan. [ABSTRACT FROM AUTHOR]

Aymé‐Gripp syndrome (AYGRPS) is a recognizable condition caused by a restricted spectrum of dominantly acting missense mutations affecting the transcription factor MAF. Major clinical features of AYGRPS include congenital cataracts, sensorineural hearing loss, intellectual disability, and a distinctive flat facial appearance. Skeletal abnormalities have also been observed in affected individuals, even though these features have not been assessed systematically. Expanding the series with four additional patients, here we provide a more accurate delineation of the molecular aspects and clinical phenotype, particularly focusing on the skeletal features characterizing this disorder. Apart from previously reported malar flattening and joint limitations, we document that carpal/tarsal and long bone defects, and hip dysplasia occur in affected subjects more frequently than formerly appreciated. [ABSTRACT FROM AUTHOR]

ABSTRACT: Osteogenesis imperfecta (OI) is a strikingly heterogeneous group of disorders with a broad range of phenotypic variations. It is also one of the differential diagnoses in bent bone dysplasias along with campomelic dysplasia and thanatophoric dysplasia and can usually be distinguished by decreased bone mineralization and bone fractures. Bent bone dysplasias also include syndromes such as kyphomelic dysplasia (MIM:211350) and mesomelic dysplasia Kozlowski‐Reardon (MIM249710), both of which have been under debate regarding whether or not they are a real entity or simply a phenotypic manifestation of another dysplasia including OI. Bruck syndrome type 2 (BRKS2; MIM:609220) is a rare form of autosomal recessive OI caused by biallelic PLOD2 variants and is associated with congenital joint contractures with pterygia. In this report, we present six patients from four families with novel PLOD2 variants. All cases had multiple fractures. Other features ranged from prenatal lethal severe angulation of the long bones as in kyphomelic dysplasia and mesomelic dysplasia Kozlowski‐Reardon through classical Bruck syndrome to moderate OI with normal joints. Two siblings with a kyphomelic dysplasia‐like phenotype who were stillborn had compound heterozygous variants in PLOD2 (p.Asp585Val and p.Ser166*). One infant who succumbed at age 4 months had a bent bone phenotype phenotypically like skeletal dysplasia Kozlowski‐Reardon (with mesomelic shortening, camptodactyly, retrognathia, cleft palate, skin dimples, but also with fractures). He was homozygous for the nonsense variant (p.Trp561*). Two siblings had various degrees of Bruck syndrome caused by the homozygous missense variant, p.His687Arg. Furthermore a boy with a clinical presentation of moderate OI had a possibly pathogenic homozygous variant p.Trp588Cys. Our experience of six patients with biallelic pathogenic variants in PLOD2 expands the phenotypic spectrum in the PLOD2‐related phenotypes. © 2017 American Society for Bone and Mineral Research. [ABSTRACT FROM AUTHOR]

Since the original description of the IARS2-related cataracts, growth hormone deficiency, sensory neuropathy, sensorineural hearing loss, skeletal dysplasia syndrome (CAGSSS; OMIM 616007) in an extended consanguineous family of French-Canadian descent, no further patients have been reported. IARS2 (OMIM 612801) encodes the mitochondrial isoleucine-tRNA synthetase which belongs to the class-I aminoacyl-tRNA synthetase family, and has been implicated in CAGSSS and a form of Leigh syndrome. Here, we report on a female Danish patient with a novel homozygous IARS2 mutation, p.Gly874Arg, who presented at birth with bilateral hip dislocation and short stature. At 3 months, additional dysmorphic features were noted and at 18 months her radiographic skeletal abnormalities were suggestive of an underlying spondyloepimetaphyseal dysplasia (SEMD). Retrospective analysis of the neonatal radiographs confirmed that the skeletal changes were present at birth. It was only with time that several of the other manifestations of the CAGSSS emerged, namely, cataracts, peripheral neuropathy, and hearing loss. Growth hormone deficiency has not (yet) manifested. We present her clinical features and particularly highlight her skeletal findings, which confirm the presence of a primary SEMD skeletal dysplasia in a growing list of mitochondrial-related disorders including CAGSSS, CODAS, EVEN-PLUS, and X-linked SEMD-MR syndromes. [ABSTRACT FROM AUTHOR]

Opsismodysplasia is an autosomal recessive skeletal disorder characterized by facial dysmorphism, micromelia, platyspondyly and retarded bone maturation. Recently, mutations in the gene encoding inositol polyphosphate phosphatase-like 1 (INPPL1) are found in several families with opsismodysplasia by a homozygosity mapping, followed by whole genome sequencing. We performed an exome sequencing in two unrelated Japanese families with opsismodysplasia and identified a novel INPPL1 mutation, c.1960_1962delGAG, in one family. The mutation is predicted to result in an in-frame deletion (p.E654del) within the central catalytic 5-phosphate domain. Our results further support that INPPL1 is the disease gene for opsismodysplasia and that opsismodysplasia has genetic heterogeneity. [ABSTRACT FROM AUTHOR]

ABSTRACT We report a case of osteogenesis imperfecta (OI) (OMIM166210) type II, in which a prenatal diagnosis was made by three-dimensional computed tomography (3D-CT). Subsequent molecular analysis revealed a recurrent, heterozygous mutation in COL1A2. Fetal CT is a powerful tool for visualizing the fetal skeleton and can provide a definitive diagnosis of fetal skeletal dysplasias; however, whether or not its employment for prenatal diagnosis is warranted in terms of fetal radiation risks remains controversial, both medically and ethically. Based on our experience, we review the current state of fetal CT for the diagnosis of skeletal dysplasias, with a discussion of the relevant literature. [ABSTRACT FROM AUTHOR]

Heterozygous COL2A1 mutations create a group of skeletal dysplasias collectively termed type II collagenopathies. Sporadic cases of type II collagenopathies are almost exclusively caused by de novo mutations. Very few cases with intrafamilial recurrence due to germinal mosaicism have been known. We report here on a family in which a severe form of skeletal dysplasia was recurrent in two sibs whose phenotype was most consistent with platyspondylic lethal skeletal dysplasia Torrance type (PLSD-T). A COL2A1 analysis showed that the two sibs had a heterozygous mutation in the encoded triple helical region of COL2A1, c.3545G>A (p.Gly1182Asp) in exon 50. The parents did not consent to a molecular analysis; however, the presence of the same mutation in the two sibs is proof of germinal mosaicism in one of the parents. PLSD-T has been shown to arise from a heterozygous dominant negative COL2A1 mutation in the encoded C-propeptide region. However, our observation suggests that the phenotype is also caused by a COL2A1 mutation in the encoded C-terminal triple helical region. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Background Brachyolmia is a heterogeneous group of skeletal dysplasias that primarily affects the spine. Clinical and genetic heterogeneity have been reported; at least three types of brachyolmia are known. TRPV4 mutations have been identified in an autosomal dominant form of brachyolmia; however, disease genes for autosomal recessive (AR) forms remain totally unknown. We conducted a study on a Turkish family with an AR brachyolmia, with the aim of identifying a disease gene for AR brachyolmia. Methods and results We examined three affected individuals of the family using exon capture followed by next generation sequencing and identified its disease gene, PAPSS2 (phosphoadenosine-phosphosulfate synthetase 2). The patients had a homozygous loss of function mutation, c.337•338insG (p.A113GfsX18). We further examined three patients with similar brachyolmia phenotypes (two Japanese and a Korean) and also identified loss of function mutations in PAPSS2; one patient was homozygous for IVS3+2delT, and the other two were compound heterozygotes for c.616-634del19 (p.V206SfsX9) and c.1309-1310delAG (p.R437GfsX19), and c.480_481insCGTA (p.K161RfsX6) and c.661delA (p.I221SfsX40), respectively. The six patients had shorttrunk short stature that became conspicuous during childhood with normal intelligence and facies. Their radiographic features included rectangular vertebral bodies with irregular endplates and narrow intervertebral discs, precocious calcification of rib cartilages, short femoral neck, and mildly shortened metacarpals. Spinal changes were very similar among the six patients; however, epiphyseal and metaphyseal changes of the tubular bones were variable. Conclusions We identified PAPSS2 as the disease gene for an AR brachyolmia. PAPSS2 mutations have produced a skeletal dysplasia family, with a gradation of phenotypes ranging from brachyolmia to spondyloepi- metaphyseal dysplasia. [ABSTRACT FROM AUTHOR]

Objective. Fetal three-dimensional helical computed tomography (3D-CT) has attracted attention in the diagnosis of fetal skeletal dysplasias because of limited diagnostic capabilities of standard ultrasonography to delineate the skeleton. Here we report the first instance of diagnosing Kniest dysplasia with 3D-CT. Methods. Fetal 3D-CT was performed for a fetus at 28 weeks' gestation after ultrasonography at 24 weeks had shown moderate shortening of the limbs, mild narrow thorax, and polyhydramnios. The imaging parameters were set so as to reduce estimated fetal irradiation dose to 12.39 mGy of the CT dose index volume and 442 of the dose length product. Results. Fetal 3D-CT revealed dumbbell-shaped femora and platyspondyly with coronal cleft of the lumbar vertebral body. This warranted a diagnosis of Kniest dysplasia and corresponded well with postnatal radiographic findings. In retrospect, however, spinal deformation was somewhat underestimated due to image smoothing associated with image processing in 3D-CT. Genetic testing for COL2A1 confirmed Kniest dysplasia; i.e., a de novo mutation of A-C transversion at the splice acceptor site of the 3′ end of intron 16. Conclusions. The combined use of 3D-CT with ultrasonography is a power tool for the prenatal diagnosis of congenital skeletal dysplasias. [ABSTRACT FROM AUTHOR]

The growth and development of the skeleton is regulated by bone morphogenetic proteins of which several are linked to genetic skeletal disorders. So far, no human skeletal malformations have been associated with variants in BMP5. Here, we report a patient with biallelic loss of function variants in BMP5 and a syndromic phenotype including skeletal dysostosis, dysmorphic features, hypermobility, laryngo‐tracheo‐bronchomalacia and atrioventricular septal defect. We discuss the phenotype in relation to the known tissue‐specific expression of Bmp5 and similar morphological abnormalities previously reported in experimental animal models. Our findings suggest a new association between BMP5 variants and a range of developmental anomalies, involving ears, heart and skeleton, thereby increasing understanding of BMP5's role in human development. [ABSTRACT FROM AUTHOR]

Transient receptor potential cation channel, subfamily V, member 4 (TRPV4) is a calcium-permeable nonselective cation channel of unknown biological function. TRPV4 mutation was first identified in brachyolmia, and then in a spectrum of autosomal-dominant skeletal dysplasias, which includes Kozlowski type of spondylometaphyseal dysplasia, metatropic dysplasia, Maroteaux type of spondyloepiphyseal dysplasia and parastremmatic dysplasia. Recently, TRPV4 mutation has also been identified in a spectrum of neuromuscular diseases that includes congenital distal spinal muscular atrophy (SMA), scapuloperoneal SMA, and hereditary motor and sensory neuropathy type IIC. These diverse spectrums of diseases compose a novel channelopathy, TRPV4-pathy, which could further include polygenic traits such as serum sodium concentration and a chronic obstructive pulmonary disease. In this review, we clarified the TRPV4 mutation spectrum, and discussed the phenotypic complexity of TRPV4-pathy and its pathogenic mechanisms. TRPV4-pathy may extend further to other monogenic and polygenic diseases. [ABSTRACT FROM AUTHOR]

Ellis-van Creveld syndrome (EvC MIM. #225500) is an autosomal recessive skeletal dysplasia characterised by thoracic hypoplasia, cardiac anomalies, acromesomelic limb shortening, and postaxial polydactyly. Affected individuals commonly manifest with cardiorespiratory failure as neonates but generally survive neonatal difficulties. We report here on affected Japanese sibs with a lethal phenotype of EvC caused by novel compound heterozygous mutations of EVC2, c.871-3 C > G and c.1991dupA. [ABSTRACT FROM AUTHOR]

We describe a novel recognizable phenotype characterized by anophthalmia, a distinctive skeletal dysplasia and intellectual disability. Radiographic anomalies include severe rhizomelic shortness of the limbs and abnormal joint formation. Recent exome studies showed that these characteristics are part of the phenotypic spectrum of MAB21L2 gene mutations which cause a range of structural eye malformations such as microphthalmia/anophthalmia and ocular coloboma. The two unrelated individuals described here in detail are heterozygous carriers of the same de novo missense mutation c.151C > T (p.Arg51Cys) in MAB21L2. [ABSTRACT FROM AUTHOR]

Kenny-Caffey syndrome (KCS) and the similar but more severe osteocraniostenosis (OCS) are genetic conditions characterized by impaired skeletal development with small and dense bones, short stature, and primary hypoparathyroidism with hypocalcemia. We studied five individuals with KCS and five with OCS and found that all of them had heterozygous mutations in FAM111A. One mutation was identified in four unrelated individuals with KCS, and another one was identified in two unrelated individuals with OCS; all occurred de novo. Thus, OCS and KCS are allelic disorders of different severity. FAM111A codes for a 611 amino acid protein with homology to trypsin-like peptidases. Although FAM111A has been found to bind to the large T-antigen of SV40 and restrict viral replication, its native function is unknown. Molecular modeling of FAM111A shows that residues affected by KCS and OCS mutations do not map close to the active site but are clustered on a segment of the protein and are at, or close to, its outer surface, suggesting that the pathogenesis involves the interaction with as yet unidentified partner proteins rather than impaired catalysis. FAM111A appears to be crucial to a pathway that governs parathyroid hormone production, calcium homeostasis, and skeletal development and growth. [Copyright &y& Elsevier]

Spondyloepimetaphyseal dysplasia with joint laxity, leptodactylic type (lepto-SEMDJL, aka SEMDJL, Hall type), is an autosomal dominant skeletal disorder that, in spite of being relatively common among skeletal dysplasias, has eluded molecular elucidation so far. We used whole-exome sequencing of five unrelated individuals with lepto-SEMDJL to identify mutations in KIF22 as the cause of this skeletal condition. Missense mutations affecting one of two adjacent amino acids in the motor domain of KIF22 were present in 20 familial cases from eight families and in 12 other sporadic cases. The skeletal and connective tissue phenotype produced by these specific mutations point to functions of KIF22 beyond those previously ascribed functions involving chromosome segregation. Although we have found Kif22 to be strongly upregulated at the growth plate, the precise pathogenetic mechanisms remain to be elucidated. [Copyright &y& Elsevier]