Biochemical and molecular studies of the cartilaginous endoskeleton of adult lampreys and hagfish
Year: 1999
Type: dissertation
Abstract: Earlier morphological and biochemical data on the cartilaginous endoskeletons of the lamprey, 'Petromyzon marinus', and the hagfish, ' Myxine glutinosa' revealed that these structures were non-collagenous and displayed similarities to vertebrate elastins. This finding was unusual in two respects, firstly other vertebrate cartilage is generally type II collagen-based, and secondly the phylogenetic distribution of elastin was thought not to extend into the jawless vertebrates. Recently we have cloned the cDNAs encoding lamprin, the major matrix protein of lamprey annular cartilage. This study revealed interesting similarities to avian and mammalian elastins as well as to some insect structural proteins. Here I extend the biochemical and molecular investigation into these agnathan endoskeletal structures to further our understanding of the basic biology of these tissues, as well as to understand the relationships between lamprin, elastin, and the insect structural proteins. In both the lamprey and hagfish I show that there are at least two types of non-collagenous cartilage matrix proteins. Although all four of these matrices show some similarities with each other, suggesting a 'family' of cartilaginous proteins, it is clear that the major matrix proteins of each are different. Molecular characterization of lamprin was extended to include its genomic organization. There are three lampfin genes in 'P. marinus', each containing 6 protein-coding exons, one of which is alternatively spliced in all three genes. 5'-upstream sequence and transcription start site determination indicate that the lamprin genes contain theoretical TATA box and CAP signal sequences. Characterization of lamprin genes from a second species of lamprey, 'Lampetra richardsoni', reveals that at least some of the lamprin genes in this species appear in tandem in a head-to-tail orientation separated by no more than 7 kb of sequence. Finally, the lack of sequence conservation of the lamprin-like sequences within the elastin and chorion genes, and the fact that no lamprin-like sequences are apparent within the hagfish cartilaginous matrix proteins, strongly suggest that the sequence similarities between lamprin, elastin, and the insect structural proteins are a result of a process of convergent evolution.
Author: Paul Robson
Language: English
Subfield: Urology
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W3127407894