Identification of novel alternatively spliced isoforms of the tropomyosin-encoding gene, TMnm, in the rat cochlea.
Analysis of a rat cochlear cDNA library for the expression of the non-muscle (nm) tropomyosin (TM)-encoding gene (TMnm), demonstrated that four nm isoforms were present. These four TMnm variants are NM-1, NM-2, NM-3 and NM-4. Nucleotide (nt) sequencing revealed that all these isoforms expressed the nm exon 1b sequence, but varied in their usage of the alternatively spliced exons 6a and b and 9a/b and d, representing skeletal muscle (sk) (exons 6b and 9a/b) and nm (6a and 9d) sequences. A novel exon 9 (designated as exon 9c) was associated with the NM-4 isoform and was also found to be expressed in the cochlea. Comparisons of the nt and amino acid (aa) sequences demonstrated a high homology between rat, mouse and human sequences encoding the 'classical' nm isoform, TM30nm, which is designated herein as NM-1. The rat NM-1 nt homology with mouse and human sequences also included the 3' untranslated region. Homologies were found between aa sequences of the C termini of NM-1 and the TM alpha smooth muscle and TM beta nm isoforms, between the sk sequence of NM-3 and the TM alpha and beta sk isoforms, and between the novel 9c sequence of NM-4 and the TM alpha brain-1 isoform. These data predict that the nm isoforms share biochemical properties described for the other TM isoforms.
Beisel
K W
KW
Center for Hereditary Communication Disorders, Boys Town National Research Hospital, Omaha, NE 68131.
Kennedy
J E
JE
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003051:Cochlea / Q000737:chemistry*; D005091:Exons; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D051381:Rats; D012689:Sequence Homology, Nucleic Acid; D014335:Tropomyosin / Q000235:genetics*
D014335:Tropomyosin