Expression of DLX3 in chick embryos

Higher vertebrates appear to possess six genes encoding a homeodomain of the distal-less type. We report the cloning and expression pattern of the chicken DLX3 gene, a homeobox gene highly related to the DLX5 gene with regard to both the encoded protein structure and the expression pattern. DLX3 RNA was observed during the development of the olfactory and otic placodes, in the distal portion of the first and second visceral arch mesenchyme, in the growing limb buds, and in the tail tip. No expression occurs in the central nervous system.     

RNA splicing: three themes with variations

We have isolated the four separate segments of chicken DNA which contain sequence homology to β tubulin. With the exception of a fifth region of DNA which appears to contain only a 5′ fragment of β gene, these four cloned sequences represent all of the β tubulin encoding DNA in the chicken. Each gene is very similar in structure, containing three or four small intervening sequences clustered in the 5′ portion of the coding region. Using RNAs prepared from a variety of cell lines and tissues, we have found five different mRNAs which carry β tubulin sequences, two of which are encoded by the same gene. Three of these mRNAs are unexpectedly long (between 3500 and 4000 bases). However, these large mRNAs do give authentic β tubulin translation products. Overall, we conclude that each of the four β tubulin genes is a functional gene which is expressed in a specific program during differentiation. These data strongly suggest that four β tubulins are necessary for proper microtubule function in vertebrates.     

Cloning and sequencing of a leech homolog to the Drosophila engrailed gene.

We have cloned and sequenced a homolog (ht-en) to the Drosophila engrailed (en) gene from the glossiphoniid leech, Helobdella triserialis. Amino acid comparisons of the ht-en homeodomain and C-terminal residues with the corresponding residues encoded by en-class genes of other species reveal 75-79% sequence identity. In addition, the ht-en sequence appears to have a serine-rich region 16 residues C-terminal from the homeodomain, which by analogy to Drosophila may be a target site for phosphorylation. The leech gene encodes some amino acid substitutions for residues that are highly conserved in other species. These are found within the second and third of the three putative helices of the homeodomain, and in both of the intervening turn regions.