Talpid2 mutant of the chicken with perturbed cartilage development has an altered precartilage-specific chromatin protein.

An abundant nonhistone protein (Mr, 125,000) is lost from the chromatin embryonic chicken precartilage mesenchyme cells as they differentiate into cartilage [Newman, SA., Birnbaum, J & Yeoh, G.C.T.(1976) Nature (London) 259, 417-418]. We have now examined the chromatin proteins of precartilage and cartilage cells of chicken embryos carrying the talpid2 gene which causes a perturbed patern of cartilage differentiation in the homozygous state. We find that homozygous talpid2 precartilage chromatin differs from that of the normal cell type in having its abundant precartilage chromatin protein decreased to a Mr of approximately 120,000 and in having a "precocious" cartilage-like pattern of proteins in the Mr 35,500-36,500 region. The precartilage chromatin of talpid2 heterozygotes is completely normal within the resolution of our techniques, as is the cartilage chromatin of the homozygote and heterozygote talpid2 embryos. The correlation of an aberration in a developmentally significant chromatin protein with the perturbed development of its tissue of origin is discussed.