These conditional targeted mutation mice carry loxP sites on either side of the first unique coding exon of the neurexin beta promoter isoforms of Nrxn1 (neurexin I), Nrxn2 (neurexin II), and Nrxn3 (neurexin III). These exons correspond to exon 18 of Nrxn1 (neurexin I), exon 17 of Nrxn2 (neurexin II), and exon 17 of Nrxn3 (neurexin III). These exons have been further modified to include green fluorescent protein (GFP) (neurexins 1 and 3), or hemagglutinin (HA) protein (neurexin 2). The GFP and HA inserts don't affect the expression of the beta neurexin genes, but it is very difficult to detect signals in the tissue by immunohistochemistry or direct fluorescence. The single, double and triple homozygous floxed mutants are fully viable, fertile, normal in size, and do not display any gross physical or behavioral abnormalities. When crossed with a Cre recombinase-expressing strain, this strain is useful in eliminating tissue-specific expression of the beta isoforms of the gene(s). This strain may be useful in studies of neuronal synaptic vesicle exocytosis.
Homozygous deletion of the beta neurexin 3 floxed segment mediated through Cre excision generates pups with normal viability and fertility; triple knockout mice are viable, but are infertile and smaller in size (~70% of wild-type in body weight).
Note: The original curations for this strain indicated that exon 1 of the Nrxn1, Nrxn2, and Nrxn3 genes were modified. Subsequent published information (Anderson, 2015) clarified that it was the first exon of the beta promoter isoforms that were targeted. (September, 2019).
