Csm, a Cardiac-specific Isoform of the RNA Helicase Mov10l1, Is Regulated by Nkx2.5 in Embryonic Heart

Tomomi Ueyama,Hideko Kasahara,Takahiro Ishiwata,Naohito Yamasaki,Seigo Izumo

doi:10.1074/jbc.m300014200

Abstract

Nkx2.5 (also called Csx) is an evolutionarily conserved cardiac transcription factor of the homeobox gene family. Nkx2.5 is required for early heart development, because Nkx2.5 null mice die before completion of cardiac looping. To identify genes regulated by Nkx2.5 in the developing heart, we performed differential screening in combination with suppression subtractive hybridization using RNA isolated from wild-type and Nkx2.5 null hearts at embryonic day 8.5. One gene that we found to be markedly down-regulated in the hearts from Nkx2.5 null embryos is an isoform of Mov10 like-1 (Mov10l1), a putative RNA helicase expressed in testis. We named this novel isoform as Csm (cardiac-specific isoform of Mov10l1). Csm is identical with the 3' region of the Mov10l1 gene, but its transcript starts from the exon 16 of Mov10l1. The conceptual protein encoded by Csm cDNA contains a helicase motif as well as ATPase and RNA interaction motifs. Csm is expressed specifically in the heart, and its expression in the heart is restricted to cardiac myocytes. Csm potentiated phenylephrine-induced hypertrophic response in cardiac myocytes. Furthermore, transient cotransfection analysis showed that Nkx2.5 transactivates the Csm promoter, suggesting that Nkx2.5 is essential for embryonic Csm expression.

Highlights

We and others have previously reported several genes downregulated in the Nkx2.5-null heart, including atrial natriuretic factor (ANF), B-type natriuretic peptide, CARP, eHAND, MEF2C, myosin light chain 2v, SM22, N-myc, Msx2, Irx4, and Chisel (6, 7, 10 –15)
One gene that we found to be markedly down-regulated in the hearts from Nkx2.5 null embryos is an isoform of Mov10 like-1 (Mov10l1), a putative RNA helicase expressed in testis
Identification of Nkx2.5-dependent Gene Csm, Cardiac-specific Isoform of Mov10l1—To identify potential target genes regulated by Nkx2.5 in the developing heart, we performed differential screening in combination with suppression subtractive hybridization using RNA from hearts of wild-type and Nkx2.5 null mice at embryonic day (ED) 8.5

Summary

Introduction

We and others have previously reported several genes downregulated in the Nkx2.5-null heart, including atrial natriuretic factor (ANF), B-type natriuretic peptide, CARP, eHAND, MEF2C, myosin light chain 2v, SM22, N-myc, Msx, Irx, and Chisel (6, 7, 10 –15). The protein encoded by this gene, named Csm, cardiacspecific isoform of Mov like-1 (Mov10l1), was markedly downregulated in the Nkx2.5 null heart. Nkx2.5 ( referred to as Csx) is a member of the NK2 class ated phenylephrine-induced hypertrophic response in cardiac of homeoproteins [1, 2]. Murine Nkx2.5 was identified as a homologue of the Drosophila tinman gene [4], which is required for subdivision of the dorsal mesoderm into the cardiac and visceral mesoderm [1, 2]. The nucleotide sequence(s) reported in this paper has been submitted to the GenBankTM/EBI Data Bank with accession number(s) AY303754

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Conclusion