Whole-exome sequencing analysis of Waardenburg syndrome in a Chinese family

Identification of a novel compound heterozygous IDUA mutation underlies Mucopolysaccharidoses type I in a Chinese pedigree

BACKGROUND

Mucopolysaccharidosis type I (MPS I) is a rare autosomal storage disorder resulting from the defective alpha-L-iduronidase (encoded by IDUA) enzyme activity and accumulation of glycosaminoglycans (GAGs) in lysosomes. So far, more than 100 IDUA causative mutations have been identified leading to three MPS I phenotypic subtypes: Hurler syndrome (severe form), Hurler/Scheie syndrome (intermediate form), and Scheie syndrome (mild form).

METHODS

Whole-exome sequencing (WES) was performed to identify the underlying genetic mutations. To verify the identified variations, Sanger sequencing was performed for all available family members following PCR amplification. The impact on IDUA protein was analyzed by sequential analysis and homology modeling.

RESULTS

A novel IDUA heterozygous single base insertion (c.1815dupT, p.V606Cfs51^* ) and a known missence mutation (c.T1037G, p.L346R) were detected in our patient diagnosed as congenital heart disease with heart valve abnormalities. The novel frameshift mutation results in a complete loss of 48 amino acids in the Ig-like domain and causes the formation of a putative protein product which might affect the IDUA enzyme activity.

CONCLUSIONS

A novel compound heterozygous IDUA mutation (c.1815dupT, p.V606Cfs51^* ) was found in a Chinese MPS I family. The identification of the mutation facilitated accurate genetic counseling and precise medical intervention for MPS I in China.

A new NOTCH3 damaging variant in a thrombocytopenia family of Miao ethnic group

BACKGROUND

Pediatric inherited thrombocytopenia, also known as a deficiency of platelets in children, is caused by genetic factors and it is hard to obtain an effective treatment. Thus, it is necessary to identify the possible genetic variants that are responsible for thrombocytopenia.

METHODS

Whole exome sequencing was used to detect genetic variants in two members of a thrombocytopenia family of Miao ethnic group. Multiple in silico analyses were performed to evaluate the effects of the novel missense variants.

RESULTS

Finally, a novel variant (chr19: g.15170364G>A) in the NOTCH3 gene was found, as confirmed with Sanger sequencing, which could result in a R1694Q substitution in the protein. This variant was consistently suggested to be damaging by sift (Sorting Tolerant From Intolerant; http://sift.jcvi.org), polyphen (Polymorphism Phenotyping, version 2.0; http://genetics.bwh.harvard.edu/pph2) and mutationtaster (http://www.mutationtaster.org) software. By building the 3D model of the key region of NOTCH3 protein and performing the structure simulation, we found that (i) this variant affected the 3D structure model with a root-mean-square deviation = 0.46 between wild-type and mutant type; (ii) this variant caused the protein to reduce the solvent accessible surface area by 421 Å² ; and (iii) compared to the wild-type protein, the mutant protein had two less amino acids to maintain protein stability.

CONCLUSIONS

A novel damaging variant in the NOTCH3 gene was identified in a thrombocytopenia family with respect to decreasing the stability of NOTCH3, which may help with the prognosis and therapy of inherited thrombocytopenia.

A novel INDEL mutation in the PTCH1 gene in a Chinese family with Gorlin syndrome

Gorlin syndrome is a rare autosomal dominant disorder, and 50% of the cases are due to the mutation of PTCH1, the major receptor of the hedgehog signaling pathway. Here we report a new Gorlin syndrome family found in Xinzhou, China. A further sequence analysis found a novel PTCH1 INDEL mutation, NM_001083602.2: c.1516_1524delinsTGAGCTGGAGCTCCG (p. Ala506*), leading an N Terminal truncated protein. This truncated PTCH1 was considered as non-functional version as it loses almost all functional domains, including the 4-12 transmembrane domains and the intracellular and extracellular domains accordingly. Although the effect of the N-terminal truncated PTCH1 is not clear, Gorlin syndrome in these cases is due to haploinsufficiency. Our report enriches the Gorlin syndrome database and will help to unveil the molecular basis of this condition.

Precision medicine in hearing loss

Precision medicine (PM) proposes customized medical care based on a patient's unique genome, biomarkers, environment and behaviors. Hearing loss (HL) is the most common sensorineural disorder worldwide and is frequently caused by a single genetic mutation. With recent advances in PM tools such as genetic sequencing and data analysis, the field of HL is ideally positioned to adopt the strategies of PM. Here, we review current and future applications of PM in HL as they relate to the four core qualities of PM (P4): predictive, personalized, patient-centered, and participatory. We then introduce a strategy for effective incorporation of HL PM into the design of future research studies, electronic medical records, and clinical practice to improve diagnostics, prognostics, and, ultimately, individualized patient treatment. Finally, specific anticipated ethical and economic concerns in this growing era of genomics-based HL treatment are discussed. By integrating PM principles into translational HL research and clinical practice, hearing specialists are uniquely positioned to effectively treat the heterogeneous causes and manifestations of HL on an individualized basis.

A novel de novo mutation in COL2A1 leading to spondyloepiphyseal dysplasia congenita in a Chinese family

Spondyloepiphyseal dysplasia congenita (SEDC) is an extremely rare autosomal dominant chondrodysplasia that is usually caused by substitution of glycine with another amino acid in the triple helical region of COL2A1. Herein, we describe a case of SEDC in a Chinese family with a novel de novo mutation in the COL2A1 gene, c.1150G>A (p.Gly384Ser), which may impair protein stability and lead to dysfunction of type II collagen.