Crk adaptor proteins are necessary for the development of the zebrafish retina

Abstract

Background:The development of the central nervous system (CNS) requires critical cell signaling molecules to coordinate cell proliferation and migration in order to structure the adult tissue. Chicken tumor virus #10 Regulator of Kinase (CRK) and CRK-like (CRKL) are adaptor proteins with pre-metazoan ancestry and are known to be required for patterning laminated structures downstream of Reelin (RELN), such as the cerebral cortex, cerebellum, and hippocampus. CRK and CRKL also play crucial roles in a variety of other growth factor and extracellular matrix signaling cascades. The neuronal retina is another highly laminated structure within the CNS that is dependent on migration for proper development, but the cell signaling mechanisms behind neuronal positioning in the retina are only partly understood.Results: We find that crk and crkl have largely overlapping expression within the developing zebrafish nervous system. We find that their disruption results in smaller eye size and loss of retinal lamination. Conclusions:Our data indicate that Crk adaptors are critical for proper development of the zebrafish neural retina in a crk/crkl dose-dependent manner.

CRK and NCK adaptors may functionally overlap in zebrafish neurodevelopment, as indicated by common binding partners and overlapping expression patterns

“…5C) [31]. Results from our previous zebrafish study suggested the possibility that another protein might compensate for genetic loss of both crk and crkl in zebrafish eye development [5]. If true, the compensating protein, possibly NCK1 or NCK2, would be one that would interact with at least one of the 46 proteins binding in common to the SH2 domains of CRK and CRKL.…”

“…We clustered the list of 29 overlapping CRK‐SH2 and NCK‐SH2 binding partners by known function and protein type (Table S1). The CNS developmental phenotypes observed with CRK adaptor loss suggest one of their primary functions in these tissues is to mediate cell motility and adhesion via scaffolding proteins [3,5]. Proteins with these functions were some of the most abundantly detected proteins using spectral counts as a proxy for abundance [55] (Fig.…”

“…Previously, we demonstrated that genetic disruption of the paralogs crk and crkl in zebrafish leads to smaller and inappropriately laminated eyes. However, these phenotypes are inherited with only about 50% penetrance [5]. This suggests that more distantly related genes functionally overlap with crk and crkl during eye development.…”

“…More recently, we identified that Crk adaptors play overlapping developmental roles in the size and lamination of the zebrafish retina [5]. Interestingly, when both family members were genetically disrupted during zebrafish development, we observed variability in the retinal lamination phenotype; approximately half of the embryos homozygous for null alleles of both crk and crkl still exhibited some manner of appropriate retinal lamination [5]. This suggests functional compensation by a similar adaptor protein in their absence.…”

“…A possible reason for this includes CRK/CRKL‐independent signaling emanating from pY‐DAB1, which may include some levels of compensation from other adaptors. More recently, we identified that Crk adaptors play overlapping developmental roles in the size and lamination of the zebrafish retina [5]. Interestingly, when both family members were genetically disrupted during zebrafish development, we observed variability in the retinal lamination phenotype; approximately half of the embryos homozygous for null alleles of both crk and crkl still exhibited some manner of appropriate retinal lamination [5].…”