Aim: To determine the possible roles of the t-complex testis expressed gene 5 (Tctex 5) on sperm functions, the full-length sequence of mRNA was studied and compared in the testis between the normal wild-type and the sterile t-haplotype mutant mice.

Methods: We applied rapid amplification of cDNA ends, Northern blot and reverse transcription polymerase chain reaction to analyze the full length of Tctex5 mRNAs isolated from testes of the wild-type and the t-haplotype mice. Reverse transcription polymerase chain reaction was used to semi-quantitatively compare expression of Tctex 5 transcripts in the 16 tissues and 9.5 day stage embryos in the wild-type mice. E-translation was applied to estimate the amino acid sequences.

Results: One long and one short transcript of Tctex5 mRNA were discovered in mouse testis of wild-type (Tctex5l^ong-+ and Tctex5^short-+) and t-haplotype (Tctex5^long-t and Tctex5^short-t) mice, respectively. Being enhanced only in the testis, Tctex5^long-t had 17 point mutations and one 15-bp-deletion in the exon 1 region, comparing with the Tctex5^long-+, whereas the Tctex5short-t was similar to the Tctex5^short-+. The short isoforms of Tctex5 mRNAs in the two models encoded exactly the same peptides, but the long isoforms did not. The estimated peptide encoded by Tctex5^long-t had significant mutations on putative sites of phosphorylation and PP1 binding.

Conclusion: We established that mutations that occur in the Tctex5 long transcript of the t-haplotype mice are important for normal sperm function, whereas the short transcript of Tctex5 might have a conserved function among different tissues.

Keywords: t-complex testis expressed gene 5, transcripts, testis, mice

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