Molecular Clone Of SG2NA And Striatin Genes And Developmental Expression Analysis In Carassius Auratus

Goldfish (Carassius auratus) has been used as a model organism in the present thesis study. From the brain tissue, I have cloned two cDNAs for both SG2NA and Striatin using RT-PCR-linked RACE. Sequence analysis reveals that the two genes are very conservative with the corresponding genes from other vertebrate species, especially at the functional motif regions. Additionally, two new alternative splicing variants of SG2NA and Striatin have been identified in the present study. Sequence alignment shows that these variants are derived from alternative splicing in a non-conserved position with 10aa and 9aa difference in SG2NA and Striatin, respectively. Interestingly, although the varied regions are very short, the unique amino acid composition make them very important due to the presence of possibly conserved phosphorylation sites and kinase binding sites. It is predicted that the splicing pattern may represent an important regulatory mechanism for generating protein isoform with new functions.The expression patterns of the SG2NA gene have been examined in nine major tissues and twelve different developmental stages in goldfish, and also four ocular tissues from goldfish and mouse. Differential expression patterns have been observed among tissues and various embryonic stages at both mRNA and protein levels. As goldfish embryonic development proceeds, SG2NA protein and mRNA display distinct fluctuation, suggesting that they are highly regulated. Such expression patterns indicate that the Striatin family may play an important role in goldfish development. The strong expression of both proteins in retina but much reduced in other ocular tissues from goldfish and mouse suggests this family is likely involved in regulation of certain types of ocular cell differentiation. The presence of ocular expression difference between goldfish and mouse suggests possible functional diversification of the genes during evolution.In the present thesis, the author also explored the expression patterns of the two genes in certain human cancer cells and retinal ganglion cells.Together, in the present thesis, two new alternative splicing variants of SG2NA and Striatin have been identified in goldfish, also the tissue-specific distribution and dynamic changes during embryonic development have been characterized, and the ocular expression patterns of SG2NA in goldfish and mouse have been established. These results have paved the way for the further exploration of their functional mechanisms regulating embryonic development, neuronal functions and metabolic homeostasis in many different tissues.