Identification of 3' splicing variants of receptor tyrosine kinase encoding gene RET in mouse and expression study of RET splicing variants in developing mouse embryo

Abstract

Human RET proto-oncogene is composed of 21 exons and encodes trans-membrane receptor tyrosine kinase. RET plays a crucial role in the development of peripheral nervous systems (PNS) and excretory system. Activating mutations of RET gene are responsible for familial multiple endocrine neoplasia and medullary thyroid carcinoma. On the other hand, inactivating mutations of RET gene cause PNS defects. Alternative splicing of sequence 3 of exon 19 of RET gene generates splicing variants. Translation of the 3 splicing variants generates several isoforms including RET9, RET43 and RET51. RET isoforms differ in their C-terminus and present distinct transforming activity in cell transfection. Differential expression of various RET isoforms were described in developing human kidney and in tumor cell lines. The mouse Ret gene was shown to contain only 20 exons and expression study of various 3 splicing variants of Ret gene in mouse is lacking. In order to study function of various Ret isoforms in mouse development, we identify the alternative spliced exon 21 in the mouse Ret gene and analyse the expression pattern of various splicing variants during mouse embryonic development. DNA sequencing of 3 end of the mouse Ret gene identified the presence of exon 21. The mouse exon 21 shares 71.7% similarity at the nucleotide level with the respective exon in human RET gene. Expression of various 3 splicing variants of Ret gene in developing mouse embryos was analysed using RT-PCR with primers specific for exons 19, 20 and 21. We showed that the Ret 3 splicing variant equivalent of human RET51 encoding variant was the only predominant Ret transcript in the developing mouse embryos from 9.5 to 14.5 d.p.c. Differential expression of different Ret isoforms during mouse embryonic development suggesting that splicing of Ret gene is developmentally regulated and different Ret isoforms may have specific function in embryonic development. EMBR