γM Crystallin Genes in the Eye Lens of a Juvenile Common Carp Cyprinus carpio: Transcription Levels and Phylogenetic Aspect.

The study was focused on determining transcription levels of γM-crystallin genes in the eye lens of a common carp Cyprinus carpio. The transcription was detected by quantitative RT-PCR, and its relative level was quantified in 5 genes of γM-crystallins and crystallin-like proteins in C. carpio aged 4, 10 and 14 months. In all age groups, the specificity of GCM1, GCM1L, GCM2L, GCM2L3 gene expression in the lenses was found. GCM2 gene expression, apart from the lenses, was also detected in the muscles, liver and brain. Analysis of the role of the amino acid sequence of the identified γM-crystallins in the formation of the refractive properties of the lens was performed based on the assessment of calculated refractive index increments. It is assumed that high values of the refractive index of the lens in C. carpio are due not so much to a relative content of amino acids in γM-crystallins as to their sequences, which ensure the tertiary packing density of these proteins, as well as by γM-crystallin concentrations. To identify conserved domains and evolutionary relationships between γM-crystallins in fish of different taxa, a multiple alignment of amino acid sequences was performed, and a phylogenetic tree was constructed using the neighbor-joining clustering method. The high level of homology, the presence of 26 conserved regions, and the phylogenetic proximity of the compared lens crystallins in the clade Teleostomi may indicate an evolutionary consolidation of the spatial structure of these proteins and their important role in the adaptation of the fish eye's optical apparatus to vision in water. [ABSTRACT FROM AUTHOR]