Rescue of an aggressive female sexual courtship in mice by CRISPR/Cas9 secondary mutation in vivo

OBJECTIVE: We had previously reported a mouse line carrying the Atypical female courtship (HoxD(Afc)) allele, where an ectopic accumulation of Hoxd10 transcripts was observed in a sparse population of cells in the adult isocortex, as a result of a partial deletion of the HoxD gene cluster. Female mice carrying this allele displayed an exacerbated paracopulatory behavior, culminating in a severe mutilation of the studs’ external genitals. To unequivocally demonstrate that this intriguing phenotype was indeed caused by an illegitimate function of the HOXD10 protein, we use CRISPR/Cas9 technology to induce a microdeletion into the homeobox of the Hoxd10 gene in cis with the HoxD(Afc) allele. RESULTS: Females carrying this novel HoxD(Del(1–9)d10hd) allele no longer mutilate males. We conclude that a brain malfunction leading to a severe pathological behavior can be caused by the mere binding to DNA of a transcription factor expressed ectopically. We also show that in HoxD(Afc) mice, Hoxd10 was expressed in cells containing glutamate decarboxylase (Gad1) and Cholecystokinin (Cck) transcripts, corroborating our proposal that a small fraction of GABAergic neurons in adult hippocampus may participate to some aspects of female courtship.