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 <italic>Atypical female courtship</italic> (<italic>HoxD</italic><italic>Afc</italic>) allele, where an ectopic accumulation of <italic>Hoxd10</italic> transcripts was observed in a sparse population of cells in the adult isocortex, as a result of a partial deletion of the <italic>HoxD</italic> 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 <italic>Hoxd10</italic> gene in <italic>cis</italic> with the <italic>HoxD</italic><italic>Afc</italic> allele. Results: Females carrying this novel <italic>HoxD</italic><italic>Del(1</italic>–<italic>9)d10hd</italic> 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 <italic>HoxD</italic><italic>Afc</italic> mice<italic>, Hoxd10</italic> was expressed in cells containing glutamate decarboxylase (<italic>Gad1)</italic> and Cholecystokinin (<italic>Cck</italic>) transcripts, corroborating our proposal that a small fraction of GABAergic neurons in adult hippocampus may participate to some aspects of female courtship. [ABSTRACT FROM AUTHOR]