Knockdown of zebrafish crim1 results in a bent tail phenotype with defects in somite and vascular development

Abstract

The Crim1 gene encodes a transmembrane protein containing six cysteine-rich repeats similar to those found in the BMP antagonist, chordin (chd). To investigate its physiological role, zebrafish crim1 was cloned and shown to be both maternally and zygotically expressed during zebrafish development in sites including the vasculature, intermediate cell mass, notochord, and otic vesicle. Bent or hooked tails with U-shaped somites were observed in 85% of morphants from 12 hpf. This was accompanied by a loss of muscle pioneer cells. While morpholino knockdown of crim1 showed some evidence of ventralisation, including expansion of the intermediate cell mass (ICM), reduction in head size bent tails and disruption to the somites and notochord, this did not mimic the classically ventralised phenotype, as assessed by the pattern of expression of the dorsal markers chordin, otx2 and the ventral markers eve1, pax2.1, tal1 and gata1 between 75% epiboly and six-somites. From 24 hpf, morphants displayed an expansion of the ventral mesoderm-derived ICM, as evidenced by expansion of tal1, lmo2 and crim1 itself. Analysis of the crim1 morphant phenotype in Tg(fli:EGFP) fish showed a clear reduction in the endothelial cells forming the intersegmental vessels and a loss of the dorsal longitudinal anastomotic vessel (DLAV). Hence, the primary role of zebrafish crim1 is likely to be the regulation of somitic and vascular development.

Crimpy inhibits the BMP homolog Gbb in motoneurons to enable proper growth control at theDrosophilaneuromuscular junction

“…Notably, Crim1 is expressed in developing motoneuron and interneuron populations in the developing mouse and chick spinal cord, although LOF studies have not addressed a neuronal function. A Crim1 homolog has also been described in zebrafish, where it is linked to vascular and somitic development (Kinna et al, 2006), and in C. elegans, where RNAi-mediated knockdown of crm-1 (cysteine-rich motor neuron protein 1) suggests a pro-BMP function in the control of body size (Fung et al, 2007). Cell culture studies provide evidence that Crim1 binds Bmp4/7 and antagonizes the production and processing of the preprotein in the Golgi (Wilkinson et al, 2003).…”

Crim1KST264/KST264 mice display a disruption of the Crim1 gene resulting in perinatal lethality with defects in multiple organ systems

“…A loss-of-function study on Crim1 has been conducted in zebrafish using antisense morpholinos (Kinna et al, 2006), and, as with the Crim1 KST264/KST264 gene-trap mouse, a pleiotrophic phenotype was observed. The Crim1 morphant fish exhibited abnormal somite patterning, smaller eyes and heads, an expansion of ventral mesoderm-derived intermediate cell mass, as well as a range of vascular defects.…”

“…The involvement of Crim1 in blood vessel biology was suggested by the observation that knockdown of Crim1 expression in human umbilical vein endothelial cells disrupted formation of vascular tubes in culture (Glienke et al, 2002). In addition, morpholino-mediated knockdown of Crim1 in the zebrafish embryo resulted in aberrant formation of the intersegmental vessels and dorsal longitudinal anastomotic vessel, further implicating Crim1 in vascular development (Kinna et al, 2006).…”

The extracellular regulation of bone morphogenetic protein signaling

“…It is not clear, however, whether this reflects the normal function of CRIM1. The phenotypes of CRIM1 knockdowns in mice and zebrafish have been difficult to interpret, and might indicate the involvement of CRIM1 in other pathways (Kinna et al, 2006;Pennisi et al, 2007;Wilkinson et al, 2007). Loss of an apparent CRIM1 homolog (CRM-1) from C. elegans actually reduces BMP signaling (Fung et al, 2007).…”