NEW GENE, NEL, ENCODING A M(R) 93-K PROTEIN WITH EGF-LIKE REPEATS IS STRONGLY EXPRESSED IN NEURAL TISSUES OF EARLY-STAGE CHICK-EMBRYOS

A new gene, nel, was isolated from a 9-day-old chick embryonic cDNA li brary. The gene encodes a protein of 835 amino acids (93,407 M(r)) con sisting of two hydrophobic domains presumed to be the signal and trans membrane sequences, a histidine rich domain, two repeats of a cysteine rich structure similar to the C-terminal domain of von Willebrand fac tor, five EGF-like repeats, and again two repeats of the cysteine rich sequence similar to the C-terminal domain of von Willebrand factor in the presumed cytoplasmic domain. The expression of the nel gene was s tudied by Northern blot and in situ hybridization analyses of chick em bryos. The mRNA of the gene was found in all tissues of 10- and 17-day -old embryos by Northern blot hybridization. Among the tissues examine d, the level in the brain was highest and increased with age. After ha tching, gene expression was retained in the brain at about the same le vel found in old embryos, increased in the retina, and disappeared fro m the other tissues. In situ hybridization with a nel gene probe revea led that the gene was strongly expressed in neural tissues such as bra in, spinal cord, and dorsal root ganglia of early embryos. Gene expres sion was observed in the mantle layer of the neurepithelium of the bra in and of the spinal cord. Gene expression in early embryos was not re stricted to the neural tissues, but was also detected in the cells aro und cartilage, myocardium, lung mesenchymal cells, and in the liver, e tc. One band of about 4.5 Kb mRNA was detected in all tissues and stag es by Northern blot hybridization analysis. The possible function of t he gene is discussed. (C) 1995 Wiley-Liss, Inc.