Mr. Peter van Heusden
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Position: | Systems Administrator |
Department: | South African National Bioinformatics Institute (SANBI) |
Faculty: | Faculty of Natural Science |
My publications in this repository | |
Tel: | 021 959 2356 |
Fax: | 021 959 2512 |
Email: | pvh@sanbi.ac.za |
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Browsing by Author "Panji, Sumir"
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Item The African Coelecanth genome provides insights into tetrapod evolution(Macmillan Publishers, 2013) Christoffels, Alan; Hesse, Uljana; Gamieldien, Junaid; Panji, Sumir; Picone, Barbara; Van Heusden, PeterThe discovery of a living coelacanth specimen in 1938 was remarkable, as this lineage of lobe-finned fish was thought to have become extinct 70 million years ago. The modern coelacanth looks remarkably similar to many of its ancient relatives, and its evolutionary proximity to our own fish ancestors provides a glimpse of the fish that first walked on land. Here we report the genome sequence of the African coelacanth, Latimeria chalumnae. Through a phylogenomic analysis, we conclude that the lungfish, and not the coelacanth, is the closest living relative of tetrapods. Coelacanth protein-coding genes are significantly more slowly evolving than those of tetrapods, unlike other genomic features. Analyses of changes in genes and regulatory elements during the vertebrate adaptation to land highlight genes involved in immunity, nitrogen excretion and the development of fins, tail, ear, eye, brain and olfaction. Functional assays of enhancers involved in the fin-to-limb transition and in the emergence of extra-embryonic tissues show the importance of the coelacanth genome as a blueprint for understanding tetrapod evolution.Item Taste and odorant receptors of the coelecanth- a gene repertoire in transition(Wiley, 2014) Picone, Barbara; Hesse, Uljana; Panji, Sumir; Van Heusden, Peter; Jonas, Mario; Christoffels, AlanG-protein coupled chemosensory receptors (GPCR-CRs) aid in the perception of odors and tastes in vertebrates. So far, six GPCR-CR families have been identified that are conserved in most vertebrate species. Phylogenetic analyses indicate differing evolutionary dynamics between teleost fish and tetrapods. The coelacanth Latimeria chalumnae belongs to the lobe-finned fishes, which represent a phylogenetic link between these two groups. We searched the genome of L. chalumnae for GPCR-CRs and found that coelacanth taste receptors are more similar to those in tetrapods than in teleost fish: two coelacanth T1R2s co-segregate with the tetrapod T1R2s that recognize sweet substances, and our phylogenetic analyses indicate that the teleost T1R2s are closer related to T1R1s (umami taste receptors) than to tetrapod T1R2s. Furthermore, coelacanths are the first fish with a large repertoire of bitter taste receptors (58 T2Rs). Considering current knowledge on feeding habits of coelacanths the question arises if perception of bitter taste is the only function of these receptors. Similar to teleost fish, coelacanths have a variety of olfactory receptors (ORs) necessary for perception of water-soluble substances. However, they also have seven genes in the two tetrapod OR subfamilies predicted to recognize airborne molecules. The two coelacanth vomeronasal receptor families are larger than those in teleost fish, and similar to tetrapods, form V1R and V2R monophyletic clades. This may point to an advanced development of the vomeronasal organ as reported for lungfish. Our results show that the intermediate position of Latimeria in the phylogeny is reflected in its GPCR-CR repertoire.