Cymric, a Maternal and Zygotic HTK-16-Like SHARK Family Tyrosine Kinase Gene, Is Disrupted in Molgula occulta, a Tailless Ascidian

We describe the cloning and expression of a nonreceptor tyrosine kinase, cymric (Uro-1), a HTK16-like (HydraTyrosineKinase-16) gene, identified in a subtractive screen for maternal ascidian cDNAs in Molgula oculata, an ascidian species with a tadpole larva. Cymric encodes a 4 kb mRNA expressed in gonads, eggs, and embryos in the tailed M. oculata, but is not detected in eggs or embryos of the closely related tailless species, M. occulta. There is a large insertion in cymric in the M. occulta genome, as shown by transcriptome and genome analyses, resulting in it becoming a pseudogene. The cymric amino acid sequence encodes a non-receptor tyrosine kinase (TK) with an N-terminal region containing two SH2 domains and five ankyrin repeats, similar to the HTK-16-like gene found in other ascidians. Thus, the ascidian cymric genes are members of the SHARK (Src-homology ankyrin-repeat containing tyrosine kinase) family of non-receptor TKs, which have been found throughout invertebrates. We show that cymric is lacking the tyrosine kinase domain in the tailless M. occulta, although the truncated mRNA is still expressed in transcriptome data. This maternal and zygotic HTK-16-like tyrosine kinase is another described pseudogene from M. occulta and appears to not be necessary for adult development.

論文本文は2025-05-15以降公開予定