Novel variants in CIITA caused type II bare lymphocyte syndrome: A case report.

BACKGROUND: Type II bare lymphocyte syndrome (BLS II) group A is a rare primary severe immunodeficiency caused by defects in CIITA, one of genes encoding transcriptional regulatory factors for MHC II molecules. OBJECTIVE: To report a Chinese boy with mutation of CIITA. METHODS: By reviewing the clinical data of the child and performing a literature search of BLS II group A. RESULTS: The patient was presented with persistent pneumonia, chronic diarrhea, urinary tract infection, rash, failure to thrive and special facial characteristics. The patient carried novel mutations in CIITA (c.1243delC, p.R415fs*2 and c.3226C>T, p.R1076W) which were identified by next-generation sequencing and confirmed by Sanger sequencing. CONCLUSIONS: This study found novel mutations in the CIITA gene of BLS II, which complemented the mutation spectrum and contributed to the diagnosis, treatment, genetic counseling and prenatal diagnosis of BLS II.

TRPS1 mutation detection in Chinese patients with Tricho-rhino-phalangeal syndrome and identification of four novel mutations.

BACKGROUND: Tricho-rhino-phalangeal syndrome (TRPS) is a rare autosomal dominant disorder characterized by craniofacial and skeletal malformations including short stature, thin scalp hair, sparse lateral eyebrows, a pear-shaped nose, and cone-shaped epiphyses. This condition is caused by haploinsufficiency or dominant-negative effect of the TRPS1 gene. METHODS: In this study, we analyzed the clinical and genetic data of five unrelated TRPS patients. They were suspected of having TRPS on the basis of clinical and radiological features including typical hair and facial features, as well as varying degrees of skeletal abnormalities. Next-generation sequencing was performed to identify variants of the TRPS1 gene in the five patients. RESULTS: In patient 1, we found a novel mutation at c.1338C>A (p.Tyr446*) (de novo). Patient 2 had a novel phenotype of hydrocephaly and Arnold-Chiari syndrome and we also found a maternally inherited novel mutation at c.2657C>A (p.Ser886*). Patient 3 had a de novo novel mutation at c.2726G>C (p.Cys909Ser) leading to more severe phenotypes. Patient 4 had a paternally inherited known mutation at c.2762G>A (p.Arg921Gln). Patient 5 with a novel phenotype of hepatopathy had a novel deletion at [GRCh37] del(8)(q23.3-q24.11) chr8:g.116,420,724-119,124,058 (over 2,700 kb). In addition, the patient 3 who harboring missense variants in the GATA binding domain of TRPS1 showed more severe craniofacial and skeletal phenotypes. CONCLUSIONS: We describe four novel mutations and two novel phenotypes in five patients. The mutational and phenotypic spectrum of TRPS is broadened by our study on TRPS mutations. Our results reveal the significance of molecular analysis of TRPS1 for improving the clinical diagnosis of TRPS.

[Analysis of SATB2 gene mutation in a child with Glass syndrome].

OBJECTIVE: To analyze the clinical characteristics and genetic basis of a child affected with Glass syndrome. METHODS: Clinical manifestations and auxiliary examination results of the child were analyzed. Potential mutation was detected with next generation sequencing and validated by Sanger sequencing. RESULTS: The child has featured growth and mental retardation, delayed speech, cleft palate, crowding of teeth, and downslanting palpebral fissures. DNA sequencing revealed a de novo heterozygous missense mutation c.1166G>A (p.R389H) in exon 8 of the SATB2 gene in the child. CONCLUSION: The heterozygous mutation c.1166G>A (p.R389H) of the SATB2 gene probably account for the Glass syndrome in the patient.

New insights from unbiased panel and whole-exome sequencing in a large Chinese cohort with disorders of sex development.

CONTEXT: Diagnosis of non-chromosomal type disorders of sex development (DSD) has long been challenging. There is still no research on overview of a large Chinese DSD cohort. OBJECTIVE: To determine the etiologic diagnosis through unbiased large-scale panel sequencing and whole-exome sequencing (WES) within a large Chinese DSD cohort. DESIGN: Patients were recruited according to the inclusion criteria of DSD. The applied panel contains 2742 known disease-causing genes, including all known diagnostic genes for DSD. METHODS: Targeted panel sequencing (TPS) was performed, and identified candidate variants were verified. Variant pathogenicities were evaluated according to established guidelines. WES was performed for randomly selected negative samples. RESULTS: This study included 125 patients. Seventy-five variants were identified by TPS and 31 variants were reported for the first time. Pathogenic and likely pathogenic variants accounted for 38.7 and 30.7%, respectively. On the basis of clinical certainty, etiologic diagnostic rates of 46.9 and 10.3% were obtained for 46,XY and 46,XX DSD patients, respectively. We reported novel candidate genes (BMPR1B, GNAS, GHR) and regions of copy number variants outside the expected DSD genotype-phenotype correlation and determined a founder mutation (SRD5A2 p.R227Q) in patients with 5α-reductase deficiency. Further WES in randomly selected negative samples identified only one among 14 negative samples as a variant of uncertain significance, indicating that WES did not improve the diagnostic rate. CONCLUSIONS: This is the first report of the applying unbiased TPS in a large Chinese cohort of patients with 46,XY and 46,XX DSD. Our findings expand the gene, mutation and phenotype spectra of the rare types of DSD in the Chinese population and provide new insight into the current understanding of the etiologies of DSD.

Evaluation of copy number variant detection from panel-based next-generation sequencing data.

BACKGROUND: Targeted gene capture and next-generation sequencing (NGS) has been widely utilized as a robust and cost-effective approach for detecting small variants among a group of disease genes. Copy number variations (CNV) can also be inferred from the read-depth information but the accuracy of CNVs called from panel-based NGS data has not been well evaluated. METHODS: Sequencing data were acquired from patients underwent routine clinical targeted panel sequencing testing. Pathogenic CNVs detected from targeted panel sequencing data were evaluated using CNVs generated by two clinical accepted platforms, namely chromosome microarray analysis (CMA) and multiple ligation-dependent probe amplification (MLPA) as benchmarks. CNVkit was used in our study to call CNVs from sequencing data using read-depth information. CMA and MLPA tests were used to confirm and further assess the size and breakpoints of CNVs. RESULTS: The size of CNVs detected using panel-based NGS data are over 300 kb. The sizes of CNVs detected are slightly larger (102.3% on average) using the NGS platform than using the CMA platform, and the size accuracy improved as the size of variants increases. The breakpoints of CNVs detected using NGS data are quite close (within 2.3% of margin) to the breakpoints detected by CMA. CNVs on sex chromosomes, however, are less concordant between NGS and CMA platforms. CONCLUSION: Copy number variations covering adequate exons on autosomes can be accurately detected using targeted panel sequencing data as using CMA. CNVs detected from sex chromosomes need further evaluation and validation. Except for exon-level deletion/duplication and CNV on sex chromosome, our data support the use of panel-based NGS data for routine clinical detection of pathogenic CNVs.

Increased transactivation and impaired repression of ß-catenin-mediated transcription associated with a novel SOX3 missense mutation in an X-linked hypopituitarism pedigree with modest growth failure.

SOX3, a transcription factor of the SRY-related high mobility group box family, has been implicated in the etiology of X-linked hypopituitarism. Here, we report a Chinese pedigree of X-linked hypopituitarism with variable phenotypes. Despite the complete growth hormone deficiency, the growth failure of the patients was relatively modest. A rare point variant of SOX3 (c.424C > A; p. P142T) was identified in the pedigree via target panel sequencing. An in vitro study showed that both the expression and nuclear targeting of SOX3 remained unaffected by the variant. However, increased transcriptional activation and impaired repression of ß-catenin-mediated transcription were noticed as a result of the SOX3 variant. This is the first study to report that the rare SOX3 missense variant associated with hypopituitarism possibly due to increased activation of SOX3 target genes and disregulation of ß-catenin target genes. In addition, we have expanded the phenotypic spectrum associated with SOX3 mutations.

Novel pathogenic ACAN variants in non-syndromic short stature patients.

BACKGROUND: Pathogenic variants of ACAN have been reported to cause spondyloepiphyseal dysplasia Kimberley type, spondyloepimetaphyseal dysplasia, familial osteochondritis dissecans and idiopathic short stature with normal to advanced bone age. A recent international cohort study significantly expanded the ACAN mutation spectrum, further delineated the heterogeneous clinical characteristics of ACAN mutation patients. The prevalence of ACAN mutation in short stature patients is yet unknown. METHODS: Here we set to assess the frequency of ACAN variants among a cohort of 218 Chinese children with non-syndromic short stature. RESULTS: We identified three novel truncating variants at the 5' end of ACAN gene. All these pathogenic variants co-segregate with severe short stature phenotype in families. In addition, none of the probands showed significant advanced bone age. All affected individuals showed no signs of significant dysmorphic features or skeletal abnormities. The prevalence of ACAN defect in this cohort is estimated to be 1.4% (3/218). It is higher among families with parents also affected with severe short stature, up to 7.0% (3/43) if parental height is <2.5 SD or 16.7% (3/18) if parental height is <3.0 SD. CONCLUSION: Our data suggest that ACAN mutation is a relative common cause of familial severe short stature.

Clinical and Molecular Characterization of Patients with Fructose 1,6-Bisphosphatase Deficiency.

Fructose-1,6-bisphosphatase (FBPase) deficiency is a rare, autosomal recessive inherited disease caused by the mutation of the FBP1 gene, the incidence is estimated to be between 1/350,000 and 1/900,000. The symptoms of affected individuals are non-specific and are easily confused with other metabolic disorders. The present study describes the clinical features of four Chinese pediatric patients who presented with hypoglycemia, hyperlactacidemia, metabolic acidosis, and hyperuricemia. Targeted-next generation sequencing using the Agilent SureSelect XT Inherited Disease Panel was used to screen for causal variants in the genome, and the clinically-relevant variants were subsequently verified using Sanger sequencing. Here, DNA sequencing identified six variations of the FBP1 gene (NM_000507.3) in the four patients. In Case 1, we found a compound heterozygous mutations of c.704delC (p.Pro235GlnfsX42) (novel) and c.960_961insG (p.Ser321Valfs) (known pathogenic). In Case 2, we found a compound heterozygous mutations of c.825 + 1G>A and c.960_961insG (both were known pathogenically). In Case 3, a homozygous missense mutation of c.355G>A (p.Asp119Asn) (reported in ClinVar database without functional study) was found. Case 4 had a compound heterozygous mutations c.720_729del (p.Tyr241GlyfsX33) (novel) and c.490G>A (p.Gly164Ser) (known pathogenically). Further in vitro studies in the COS-7cell line demonstrated that the mutation of ASP119ASN had no impact on protein expression, but decreased the enzyme activity, and with which the clinical significance of Asp119Asn can be determined to be likely pathogenic. This report not only expands upon the known spectrum of variation of the FBP1 gene, but also deepens our understanding of the clinical features of FBPase deficiency.