Construction and identification of mouse model with conditional knockout of p75 neurotrophin receptor gene in epidermal cells by Cre-loxP system

Objective To construct and identify a mouse model with conditional knockout (cKO) of p75 neurotrophin receptor (p75NTR-cKO) gene in epidermis cells by Cre-loxP system. Methods Five p75NTR^flox/flox transgenic C57BL/6J mice (aged 6-8 weeks, male and female unlimited, the age and sex of mice used for reproduction were the same below) and five keratin 14 promotor-driven (KRT14-) Cre^{+ /-} transgenic C57BL/6J mice were bred and hybridized via Cre-loxP system. Five p75NTR^flox/+ ·KRT14-Cre^{+ /-} mice selected from the first generation of mice were mated with five p75NTR^flox/flox mice to obtain the second generation hybrids. After the second generation mice were born 20-25 days, the parts of the mice tail were cut off to identify the genotype by polymerase chain reaction method. Four p75NTR gene complete cKO mice (6 weeks old) and 4 wild-type mice (6 weeks old) were selected and sacrificed respectively. The abdominal skin tissue and brain tissue were excised to observe the expression of p75NTR in the two tissue of two types of mice by immunohistochemical staining. The abdominal skin tissue of two types of mice was obtained to observe the histomorphological changes by hematoxylin and eosin staining. Results (1) Twenty second generation mice were bred. The genotype of 4 mice was p75NTR^flox/flox·KRT14-Cre^{+ /-}(p75NTR^-/-), i. e. p75NTR gene complete cKO mice; the genotype of 5 mice was p75NTR^flox/+ ·KRT14-Cre^{+ /-}, i. e. p75NTR gene partial cKO mice; the genotype of 5 mice was p75NTR^flox/flox·KRT14-Cre^-/-, and that of 6 mice was p75NTR^flox/+ ·KRT14-Cre^-/-, all of which were wild-type mice. (2) The expression of p75NTR was negative in skin epidermis tissue of p75NTR gene complete cKO mice, while numerous p75NTR positive expression was observed in skin epidermis tissue of wild-type mice. Abundant p75NTR positive expression was observed in brain tissue of both wild-type mice and p75NTR gene complete cKO mice. (3) There was no abnormal growth of skin epidermis tissue in both wild-type mice and p75NTR gene complete cKO mice, with intact hair follicle structure. Conclusions Applying Cre-loxP system can successfully construct a p75NTR-cKO mice model in epidermis cells without obvious changes in skin histomorphology.