Kristen M. Huang

Novel mutations in 13 probands with galactokinase deficiency

Galactokinase is an essential enzyme in the metabolism of galactose. Patients with deficiencies in galactokinase exhibit early‐onset cataracts. We examined the sequence of the human galactokinase gene (GK1) from 13 patients exhibiting galactokinase deficiency and identified 12 novel mutations. One of the mutations occurred in six of the 13 probands examined, and the remaining 11 were unique mutations. Expression of each of the mutant GK1 genes in Xenopus oocytes resulted in very low galactokinase activity levels. These results provide important information regarding the types of GK1 mutations that occur in the human population. Hum Mutat 15:447–453, 2000.

MiRNA expression in the eye.

MiRNAs are a newly discovered class of small noncoding RNAs that regulate gene expression by translational repression and mRNA degradation. It has become evident that miRNAs are involved in many important biological processes, including tissue differentiation and development. The role of miRNAs in the eye is beginning to be explored following their recent detection by miRNA expression analyses. Many of the target genes for these ocular miRNAs remain undefined. This review summarizes the current information about ocular miRNA expression. Future research should focus on the function of ocular miRNAs in eye development.

Genomic Profiling of miRNAs in Two Human Lens Cell Lines

Purpose: Many miRNAs are expressed in a developmentally regulated and tissue-specific manner making them crucial for tissue development in a structure such as the eye. Since miRNA target function studies for the eye will need to be performed in ocular tissue culture cells, it is important to profile them for miRNA expression. Two commonly used human lens epithelial cell lines, HLE-B3 and SRA01/04, were profiled for miRNA. Materials and Methods: We performed miRNA profiling of two commonly used lens epithelial cell lines, HLE-B3 and SRA01/04. The differential expression levels detected for miR-184 and miR-31 were confirmed by qRT-PCR and the function of a predicted miR-184 target binding site was validated in-vitro. Results: We found that four miRNAs—miR-31, miR-124, miR-184, and miR-222—were differentially expressed between the two cell lines. We show that miR-184 binds to BIN3 3′ UTR and while BIN3 mRNA expression was equal in both cell lines, the protein expression was inversely correlated with miR-184 expression. Conclusion: The differences observed with respect to miRNA expression between two different lens epithelial cell lines were minimal. Still, caution will need to be exercised when choosing one cell line over another because of the expression differences for some miRNAs. Our results also suggest that miR-184 may regulate lens BIN3 expression in lens by a miRNA-mediated translational repression mechanism.

Genetic and phenotypic analysis of Tcm, a mutation affecting early eye development

Tcm (total cataract with microphthalmia) is an autosomal dominant mouse eye mutation. Heterozygous Tcm/+ mice are born with several eye malformations including microphthalmia, retinal and iris dysplasia, total lens cataract, and ventral coloboma. The Tcm mutation was previously mapped to a 26-Mb region on Chr 4 between D4Mit235 and D4Mit106. In this study, we characterize the Tcm/Tcm homozygous mutant and find they are viable but severely microphthalmic. The developing eye in the Tcm/Tcm homozygote shows defects during early eye development, before formation of the optic cup. Further genetic mapping reduced the Tcm critical region to a 1.3-Mb region bordered by SNPs rs3666764 and rs3713818. This critical region contains two known genes (Asph and Gfd6) and three predicted genes, all of which are positional candidates for Tcm. Sequence analysis of Tcm genomic DNA revealed no mutations in the coding regions and splice site junctions of the five candidate genes. These results indicate that the causitive Tcm mutation falls within a noncoding regulatory region of one of the five candidate genes or in an undescribed gene.