Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.10.3.1 (tyrosinase)
 9,065 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The coat colour in mammals is determined by the relative amounts of eumelanin (black/brown) and phaeomelanin (red/yellow), produced in melanocytes, which are controlled by melanocyte stimulating hormone receptor (MSH-R). Melanocyte stimulating hormone receptor is activated by alpha-melanocyte-stimulating hormone (alpha-MSH). Stimulated MSH-R activates adenylyl cyclase (AC), thereby increasing the amount of cyclic AMP in the cell, which activates the enzyme tyrosinase resulting in eumelanin synthesis. In this study the complete coding sequences of five alleles of the MSH-R gene found in Holstein, Red Holstein, Simmental, and Brown Swiss cattle were cloned into a mammalian expression vector and transfected into human embryonic kidney (HEK) 293 cells. The expressed receptors were analyzed for their ability to increase intracellular cAMP in response to stimulation by alpha-MSH. The recessive red allele (e) found in Red Holstein and Simmental and the dominant black allele (ED) found in Holstein were unresponsive to a wide range of alpha-MSH concentrations. Two alleles from Brown Swiss (E(d1), E(d2)) and one allele found in the Simmental breed (e(f)) responded to stimulation by alpha-MSH in a dose-dependent manner. When compared to E(d1) and E(d2), the cells transfected with the e(f) MSH-R allele, however, reached the corresponding intracellular cAMP concentrations at a 10-fold higher concentration of alpha-MSH. In conjunction with the mode of inheritance of coat colour, the results indicate that the e MSH-R allele is a non-functional receptor, E(D) is constitutively activated receptor, and E(d1) and E(d2) are hormonally activated receptors. The delay in e(f) MSH-R response may explain the similarity between the e and e(f) phenotypes.
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PMID:Molecular and pharmacological characterisation of the MSH-R alleles in Swiss cattle breeds. 1250 31

Coat colours in cattle have been of interest to both breeders and researchers as genes regulating pigmentation not only affect the phenotype but also have economic implications in the event of genetic mutations. The genes controlling pigmentation act as a complex and interact with each other to cause phenotypic and genotypic variations. Pigmentation of coat broadly depends on the ratio of eumelanin and pheomelanin, the two components of melanin. Increase in eumelanin imparts a black coat colour while raise in pheomelanin is responsible for a yellowish or reddish colour. The main enzymes responsible for melanogenesis are regulated by the genes of the tyrosinase family. It is speculated that the wild-type gene present in the ancestral breeds of the present day cattle have more pheomelanin content and that, over time, mutations have introduced more variations leading to many shades. This could have occurred either because of interactions or because of deletions in the responsible genes. The environmental conditions have also contributed to mutations in these genes, helping in the adaptability of the animals to different geographical regions. The switching between the syntheses of melanin components depends on several genes like melanocortin-1receptor gene (MC1r) - also known as melanocyte-stimulating hormone receptor gene (MSHr)-, agouti (A), attractin (Atrn) and mahogunin (Mgrn1). The purpose of this review is to summarize the recent advances in the field of pigment biology and to highlight possible areas of research that may benefit a breeder or a farmer in the selection of animals on the basis of phenotype.
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PMID:Biology of epidermal and hair pigmentation in cattle: a mini-review. 1799 Nov 56