Involvement of GDF6 in Oculo-Skeletal Development

Abstract

Purpose:: To determine the broader role of Growth differentiation factor 6 (GDF6), a member of the bone morphogenetic protein (BMP) family, in ocular and systemic development.

Methods:: Guided by initial results illustrating GDF6’s involvement in eye development (Asai-Coakwell et al., ARVO, 2006) parallel analyses of GDF6 function were undertaken in patients and zebrafish. A panel of patients with ocular (n=58) and skeletal (n=74) phenotypes was screened for GDF6 mutations, with a subset (n=20) screened for copy number changes using qPCR. Splice-blocking morpholinos were used to inhibit zebrafish gdf6a expression, the resultant phenotypes were documented at multiple developmental stages and whole mount in situ hybridization performed with markers of somite development (fgf8, myod, unc45, mespb, her7).

Results:: Two GDF6 mutations have been identified to date in patients with ocular and/or skeletal anomalies. Morpholino inhibition of gdf6a results in a spectrum of phenotypes [ocular phenotypes present in ~60% of morphants; ocular and skeletal phenotypes, 19%] and larger morpholino doses were associated with both groups of phenotypes. In situ hybridizations with unc45 showed perturbation of somite boundaries.

Conclusions:: These findings extend the number of BMPs that are known to contribute to ocular and skeletal development. The phenotypic variability observed in some patients and zebrafish indicate involvement of other factors, and the preliminary morpholino-derived correlation between gdf6a dosage and phenotype is being clarified by ongoing experiments. Finally, the presence of ocular and skeletal phenotypes may represent a clinical marker for the patient subset with phenotypes attributable to GDF6.

Keywords: retinal development • genetics • in situ hybridization