Xiumin Wang

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.

Proband-only medical exome sequencing as a cost-effective first-tier genetic diagnostic test for patients without prior molecular tests and clinical diagnosis in a developing country: the China experience

PurposeTo evaluate the performance of proband-only medical exome sequencing (POMES) as a cost-effective first-tier diagnostic test for pediatric patients with unselected conditions.MethodsA total of 1,323 patients were tested by POMES, which targeted 2,742 known disease-causing genes. Clinical relevant variants were Sanger-confirmed in probands and parents. We assessed the diagnostic validity and clinical utility of POMES by means of a survey questionnaire.ResultsPOMES, ordered by 136 physicians, identified 512 pathogenic or likely pathogenic variants associated with over 200 conditions. The overall diagnostic rate was 28.8%, ranging from 10% in neonatal intensive care unit patients to over 35% in pediatric intensive care unit patients. The test results had an impact on the management of the 45.1% of patients for whom there were positive findings. The average turnaround time was 57 days; the cost was

Clinical characteristics and follow-up of 5 young Chinese males with gonadotropin-releasing hormone deficiency caused by mutations in the KAL1 gene.

360/case.ConclusionWe adopted a relatively efficient and cost-effective approach in China for the molecular diagnosis of pediatric patients with suspected genetic conditions. While training for clinical geneticists and other specialists is lagging behind in China POMES is serving as a diagnostic equalizer for patients who do not normally receive extensive clinical evaluation and clinical diagnosis prior to testing. This Chinese experience should be applicable to other developing countries that are lacking clinical, financial, and personnel resources.

Clinical and molecular genetic characterization of two patients with mutations in the phosphoglucomutase 1 (PGM1) gene

Isolated gonadotropin-releasing hormone (GnRH) deficiency (IGD) pertains to a group of genetic disorders consisting of anosmic hypogonadotropic hypogonadism (Kallmann syndrome, KS) and normosmic idiopathic hypogonadotropic hypogonadism (nIHH). KS is genetically heterogeneous. We hereby present 5 young male patients with GnRH deficiency caused by mutations in the KAL1 gene. Their ages ranged from 9 months to 16 years. They were referred to our department for an endocrine consultation for micropenis. Hormone assays showed low circulating gonadotropins and testosterone. Molecular studies revealed KAL1 mutations in all cases, three reported nonsense sequence variants in the KAL1 gene were detected in 4 patients, respectively (c.784C > T (p.Arg 262*), c.1267C > T (p.Arg423*), and c.1270C > T (p.Arg424*)), and one patient harbored a novel hemizygous sequence variant [c.227G > A (p.Trp76*)]. Only one patient presented short stature without growth hormone deficiency and anosmia. Another patient had bilateral eyelid ptosis, trichiasis, and refractive error. This is the first report on the co-occurrence of a KAL1 gene mutation and tent-like upper lip in four patients. All of our cases had normal olfactory bulbs and showed no renal agenesis, cleft lip/palate, and hearing impairment. These cases expand our knowledge of the phenotype associated with KAL1 sequence variations, although the precise mechanism by which KAL1 gene influences the development of this phenotype is still unknown.

Exome Sequencing Identifies De Novo DYNC1H1 Mutations Associated With Distal Spinal Muscular Atrophy and Malformations of Cortical Development

Abstract Background The phosphoglucomutase 1 (PGM1) enzyme plays a central role in glucose homeostasis by catalyzing the inter-conversion of glucose 1-phosphate and glucose 6-phosphate. Recently, PGM1 deficiency has been recognized as a cause of the congenital disorders of glycosylation (CDGs). Methods Two Chinese Han pediatric patients with recurrent hypoglycemia, hepatopathy and growth retardation are described in this study. Targeted gene sequencing (TGS) was performed to screen for causal genetic variants in the genome of the patients and their parents to determine the genetic basis of the phenotype. Results DNA sequencing identified three variations of the PGM1 gene (NM_002633.2). Patient 1 had a novel homozygous mutation (c.119delT, p.Ile40Thrfs*28). In patient 2, we found a compound heterozygous mutation of c.1172G>T(p.Gly391Val) (novel) and c.1507C>T(p.Arg503*) (known pathogenic). Conclusions This report deepens our understanding of the clinical features of PGM1 mutation. The early molecular genetic analysis and multisystem assessment were here found to be essential to the diagnosis of PGM1-CDG and the provision of timely and proper treatment.

De Novo Mutation of KAT6B Gene Causing Atypical Say–Barber–Biesecker–Young–Simpson Syndrome or Genitopatellar Syndrome

Exome sequencing has become a formidable tool for identifying potential de novo variants in causative genes of human diseases, such as neurodegenerative disorders. This article describes a 16-month-old girl with spinal muscular atrophy with lower extremity predominance and a 13-month-old girl with malformations of cortical development. Exome sequencing identified a novel de novo heterozygous missense mutation c.3395G>A (p.Gly1132Glu) and a previously reported de novo heterozygous missense mutation c.10151G>A (p.Arg3384Gln) in the DYNC1H1 gene. Bioinformatics predictions for c.3395G>A and c.10151G>A indicated pathogenicity of the mutations. DYNC1H1 is a pivotal component of cytoplasmic dynein complex, which is a microtubule-related motor involved in retrograde transport. Previous studies indicated that mutant dynein showed decreased run-length of the motor proteins and diminished retrograde transport, which were clearly associated with neuronal death and neurologic diseases. The present findings expand the mutational spectrum of the DYNC1H1 gene, reemphasizing the significance of the DYNC1H1 protein in the functioning of neurons.

Biallelic mutations in GPD1 gene in a Chinese boy mainly presented with obesity, insulin resistance, fatty liver, and short stature

ABSTRACT Mutations in KAT6B gene are responsible for Say–Barber–Biesecker–Young–Simpson syndrome (SBBYSS) and genitopatellar syndrome (GPS), with most mutations occurring in exon 18. A 4-year-old Chinese boy presented with short stature but no other clinical features of SBBYSS or GPS had a de novo novel nonsense pathogenic mutation in exon 14 of the KAT6B gene at position c.2636T>A (p.Leu879X). The correlation analysis of genotype–phenotype indicated distinctive clinical features (short stature, growth hormone deficiency, and delayed bone age) compared with the classical mutations of KAT6B gene. To the best of our knowledge, this is the first report of KAT6B gene mutation in any Chinese individual. This work expands the mutant phenotypic spectrum of the KAT6B gene.

Description of the molecular and phenotypic spectrum of Wiedemann-Steiner syndrome in Chinese patients

Biallelic mutations in the GPD1 gene cause a rare autosomal recessive inherited disease known as transient infantile hypertriglyceridemia (OMIM #614480). To date, only five pathogenic variants have been reported in 15 patients from three studies. The clinical symptoms of the affected individuals present a certain degree of heterogeneity. Here, we describe a chinese adolescent patient who mainly presented with obesity, insulin resistance, fatty liver, and short stature. Targeted next‐generation sequencing revealed a novel compound heterozygous variant in GPD1 gene (c.220‐2A>G and c.820G>A; p.Ala274Thr). In vitro studies demonstrated that the Ala274Thr variant induced a decrease in GPD1 protein expression. Further in vitro investigation of the splicing pattern in a minigene construct in HEK293 cells showed that the c.220‐2A>G variant generated an altered transcript with one cryptic splice site in exon 3, resulting in the loss of 69 bases in exon 3 (c.220_288del, p.74_96del). This is the first report involving an Asian who harbored GPD1 mutations. Our work not only expands the mutant spectrum of the GPD1 gene but also provides new insights on its resulting phenotype.

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

BackgroundWiedemann–Steiner syndrome (WDSTS) is a rare genetic disorder characterized by facial gestalt, neurodevelopmental delay, skeletal anomalies and growth retardation, which is caused by variation of KMT2A gene. To date, only 2 Chinese WDSTS patients have been reported. Here, we report the phenotypes and KMT2A gene variations in 14 unrelated Chinese WDSTS patients and investigate the phenotypic differences between the Chinese and French cohorts. MethodsNext generation sequencing was performed for each patient, and the variants in the KMT2A gene were validated by Sanger sequencing. The phenotypes of 16 Chinese WDSTS patients were summarized and compared to 33 French patients.ResultsGenetic sequencing identified 13 deleterious de novo KMT2A variants in 14 patients, including 10 truncating, 2 missenses and 1 splicing variants. Of the 13 variants, 11 are novel and two have been reported previously. One of the patients is mosaic in the KMT2A gene. The variation spectra and phenotypic profiles of the Chinese WDSTS patients showed no difference with patients of other ethnicities; however, differ in the frequencies of several clinical features. We demonstrated that variations in the KMT2A gene can lead to both advanced and delayed bone age. We identified 6 novel phenotypes, which include microcephaly, deep palmar crease, external ear deformity, carpal epiphyseal growth retardation, dyslipidemia, and glossoptosis. In addition, patients harbored missense variants in the CXXC zinc finger domain of KMT2A showed more severe neurophenotypes.ConclusionOur study consists of the largest cohort of Chinese WDSTS patients that continues to expand the WDSTS phenotypic and variation spectrum. Our results support the notion that the CXXC zinc finger domain of KMT2A gene is a hotspot for missense variants associated with more severe neurophenotypes.

A rare unbalanced Y:autosome translocation in a Turner syndrome patient

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 β-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 β-catenin target genes. In addition, we have expanded the phenotypic spectrum associated with SOX3 mutations.