Identification of a novel three-nucleotide duplication in ECM1 in Chinese siblings affected with lipoid proteinosis.

Lipoid proteinosis (LP) is a rare autosomal recessive disorder caused by pathological mutations in the glycoprotein extracellular matrix protein 1 gene (ECM1). In this study, we examined two sibling patients who were suspected of LP in a consanguineous Chinese family for clinical manifestations and sequenced the all coding exonic regions of ECM1 in the proband. Both siblings were detected a homozygous three-nucleotide duplication, c.506_508dupCTG in the exon 6 of ECM1. This mutation introduces an alanine addition between two highly conserved amino acids (Pro169 and Gly170), designated as p.169_170insA, within one of the two tandem repeat domains which are functional important for protein-protein interactions. Their parents were unaffected and heterozygous for this mutation. This mutation wasn't found in one hundred normal Chinese individuals screened and wasn't previously reported elsewhere, excluding it as a common neutral polymorphism. These evidences supported this duplication as the causative mutation of LP. Our finding expanded the spectrum of disease-causing mutations in LP and provides further evidence for the importance of ECM1 gene in the development of this rare genodermatosis.

[A novel indel NF1 mutation identified in a patient with neurofibromatosis type 1].

OBJECTIVE: To identify the genetic etiology in a Chinese patient with neurofibromatosis type 1 (NF-1). METHODS: All coding exons and the flanking sequences of neurofibromin 1 (NF1) gene from the patient were captured, individually barcoded and subjected to HiSeq2000 high-throughput sequencing. Suspected mutation was validated in the nuclear family members with Sanger sequencing. RESULTS: A novel indel mutation, c.789_790delAGinsT, was identified in the exon 8 of the NF1 gene in the patient but not in her asymptomatic parents. The mutation was predicted to have caused shifting of the reading frame and a premature downstream stop codon (p.K263Nfs*18). Two known polymorphisms, c.888+108 C>T (rs2953000) and c.888+118 G>T (rs2952999), was detected in the flanking of the indel mutation in the patient and her father. Sequencing chromatogram for the family indicates that above changes are located on the same chromosome. CONCLUSION: The c.789_790delAGinsT, as a de novo mutation occurring on the paternally derived chromosome, is most likely to be causative for the disease. Compared with Sanger sequencing, targeted next-generation sequencing is more efficient and can dramatically reduce the cost for the genetic testing of NF-1.

Identification of a novel mutation and a de novo mutation in DKC1 in two Chinese pedigrees with Dyskeratosis congenita.

Dyskeratosis congenita (DKC) is a rare and fatal congenital syndrome characterized by the triad of reticular skin pigmentation, nail dystrophy and mucosal leukoplakia, and the predisposition to bone marrow failure and malignancies. Mutations in DKC1 gene encoding dyskerin are responsible for the X-linked dyskeratosis congenita. Here we report mutation analysis of two Chinese pedigrees with dyskeratosis congenita. The 15 coding exons of DKC1 and their flanking regions were amplified from genomic DNA by PCR. DNA sequencing and restriction endonuclease digestion were used for mutation detection. Transition mutation of 1226C-->T (P409L) found in the first pedigree is a novel mutation. In the second pedigree, the proband's mother phenotypically normal carried a de novo transition mutation of 1058C-->T (A353 V) in one allele, and transmitted the mutant allele to her two sons who had typical manifestations of dyskeratosis congenita.