• MC5R belongs to the family of guanine nucleotide-protein coupled receptors(GPCRs) and are composed of an intracellular carboxylic domain, seven transmembrane helices connected by intracellular and extracellular loops, and an extracellular amino terminus.
• MC5R belongs to the melanocortins, which are a family of neuropeptide hormones and as a key part of the neuroimmunoendocrine axis.
• MC5R is widely expressed in both central nervous system and a number of peripheral organ systems.
• MC5R plays a key role in governing immune reaction and inflammatory response, and is pivotal for the regulation of sexual behavior, thermoregulation, and exocrine secretion, like sebogenesis, lacrimal secretion and release of sex pheromones..
• The exon 2 of mouse MC5R gene that encodes the full-length protein was replaced by human MC5R exon 2 in B-hMC5R mice.

Gene targeting strategy for B-hMC5R mice. The exons 2 of mouse Mc5r gene that encode signal peptide, extracellular domain, transmembrane domain, cytoplasmic region and 3’UTR are replaced by human counterparts in B-hMC5R mice. The promoter and 5’UTR region of the mouse gene are retained. The human MC5R expression is driven by endogenous mouse Mc5r promoter, while mouse Mc5r gene transcription and translation will be disrupted. 

Western blot analysis of MC5R protein expression in homozygous B-hMC5R mice. Various tissue lysates were collected from wild-type C57BL/6 mice (+/+)  and homozygous B-hMC5R mice (H/H), and then analyzed by western blot with anti-MC5R antibody(abcam, ab133656). 40 μg total proteins were loaded for western blotting analysis. MC5R was detected in lung, stomach, kidney brain and testis.

Strain specific analysis of MC5R mRNA expression in wild-type C57BL/6 mice and B-hMC5R mice by RT-PCR. Brain RNA were isolated from wild-type C57BL/6 mice (+/+) and homozygous B-hMC5R mice (H/H), then cDNA libraries were synthesized by reverse transcription, followed by PCR with mouse or human MC5R primers. Mouse Mc5r mRNA were detectable only in wild-type C57BL/6 mice. Human MC5R mRNA was detectable only in homozygous B-hMC5R mice but not in wild-type mice.