Yihua Zhu

Identification of miRNAs associated with tumorigenesis of retinoblastoma by miRNA microarray analysis

IntroductionMicroRNAs (miRNAs) are small (∽22 nucleotides) regulatory RNAs which play fundamental roles in many human diseases, including cancer. There is no report on the miRNA expression profile of retinoblastoma.MethodsThis work was undertaken to identify differentially expressed miRNAs in human retinoblastoma tissues by microRNA microarray technique, and some miRNAs were verified using northern blot analysis and the in situ hybridization method.ResultsA cluster of microRNAs was identified as highly expressed in retinoblastoma, including hsa-miR-494, hsa-let-7e, hsa-miR-513–1, hsa-miR-513–2, hsa-miR-518c*, hsa-miR-129–1, hsa-miR-129–2, hsa-miR-198, hsa-miR-492, hsa-miR-498, hsa-miR-320, hsa-miR-503, and hsa-miR-373*.ConclusionThese miRNAs are the first to be reported for human retinoblastoma and may play significant roles in regulating tumor genesis.

Confirmation of the mitochondrial ND1 gene mutation G3635A as a primary LHON mutation

We report the clinical and genetic characterization of two Chinese LHON families who do not carry the primary LHON-mutations. Mitochondrial genome sequence analysis revealed the presence of a homoplasmic ND1 G3635A mutation in both families. In Family LHON-001, 31 other variants belonging to the East Asian haplogroup R11a were identified and in Family LHON-019, 37 other variants belonging to the East Asian haplogroup D4g were determined. The ND1 G3635A mutation changes the conversed serine110 residue to asparagine. This mutation has been previously described in a single Russian LHON family and has been suggested to contribute to increased LHON expressivity. In addition, a mutation in cytochrome c oxidase subunit II at C7868T (COII/L95F) may act in synergy with G3635A, increasing LHON expressivity in Family LHON-001, which had a higher level of LHON penetrance than Family LHON-019. In summary, the G3635A mutation is confirmed as a rare primary pathogenic mutation for LHON.

Novel A14841G mutation is associated with high penetrance of LHON/C4171A family

We report the clinical and genetic characterization of a Chinese LHON family carrying an ND1/C4171A mutation. This family has high penetrance of visual impairment and extremely low frequency of vision recovery, which is in marked contrast to previously reported results for Korean LHON families with the same mutation. Sequence analysis of the complete mtDNA in the partially defined East Asian haplogroup N9a1 revealed the presence of 29 other variants. A novel heteroplasmic A14841G mutation, one of the variants with a serine substituted for a highly conserved asparagine at amino acid 32 of Cytochrome b (Cytb), may play a synergistic role with the C4171A mutation, leading to significantly different clinical manifestations of LHON among these families. The study further confirmed that C4171A was a rare primary LHON mutation, and the mtDNA background could also contribute to the clinical manifestation of the LHON/C4171A mutation.

Identification of candidate cancer genes involved in human retinoblastoma by data mining.

ObjectiveThe objective of this study was to discover potential cancer-related genes involved in retinoblastoma (RB) tumorigenesis.Materials and methodsUsing a data-mining tool called cDNA Digital Gene Expression Displayer (DGED) and serial analysis of gene expression DGED from the Cancer Genome Anatomy Project (CGAP) database, eight cDNA libraries and five serial analysis of gene expression libraries from retinoblastoma (RB) solid tumors and normal retina tissues were analyzed. The deregulated genes were classified into major families using information from Gene Ontology. Several candidate cancer-related genes were analyzed by real-time reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC) on tissue microarrays (TMA) of RB and human normal retina samples.ResultsA total of 260 genes with deregulated expression emerged when examined by DGED from the CGAP database. Functional classification of these genes not only provided an interesting insight into RB tumorigenesis but also facilitated target identification for RB therapeutics. Several candidate genes were confirmed by real-time RT-PCR and IHC analysis on TMA and were found to be associated with RB genesis through text-mining in Information Hyperlinked over Proteins. The results also implicated MCM7 and WIF1 as promising therapeutic targets for RB, but further validation is needed.

Identifcation of a Novel Mutation p.I240T in the FRMD7 gene in a Family with Congenital Nystagmus

Congenital Nystagmus (CN) is a genetically heterogeneous ocular disease, which causes a significant proportion of childhood visual impairment. To identify the underlying genetic defect of a CN family, twenty-two members were recruited. Genotype analysis showed that affected individuals shared a common haplotype with markers flanking FRMD7 locus. Sequencing FRMD7 revealed a T > C transition in exon 8, causing a conservative substitution of Isoleucine to Tyrosine at codon 240. By protein structural modeling, we found the mutation may disrupt the hydrophobic core and destabilize the protein structure. We reviewed the literature and found that exons 2, 8, and 9 (11.4% of the sequence of FRMD7 mRNA) represent the majority (55.3%) of the reported FRMD7 mutations. In summary, we identified a novel mutation in FRMD7, showed its molecular consequence, and revealed the mutation-rich exons of the FRMD7 gene. Collectively, this provides molecular insights for future CN clinical genetic diagnosis and treatment.

A novel de novo duplication mutation of PAX6 in a Chinese family with aniridia and other ocular abnormalities

Aniridia is a congenital panocular disorder caused by the mutations of the paired box gene-6 (PAX6). To investigate the clinical characterization and the underlying genetic defect in a Chinese family with aniridia and other ocular abnormalities, we recruited the family members who underwent ophthalmic examination. Two patients in this family, the proband and his affected son, both have bilateral aniridia, foveal hypoplasia and nystagmus. Moreover, the proband also had presenile cataracts, but his affected son did not show cataracts at the time of examination. Sequencing PAX6 revealed that a heterozygous duplication mutation c.95_105dup11, predicted to generate non-functional truncated protein at position Gly36 (p.G36X), was found in the affected individuals but not in any of the unaffected family members including the parents of the proband. Haplotype analysis showed that the proband and his affected son shared a common disease-related haplotype, which was arisen from the probands unaffected father through crossing-over. In conclusion, we identified a novel de novo duplication mutation of PAX6 in the aniridia and other ocular abnormalities family. This mutation has occurred de novo on a paternal chromosome by direct duplication, which presumably results from replication slippage or unequal non-sister chromatids exchange during spermatogenesis.