B6.129S1(Cg)-Rai1^tm2.1Luo/J

Stock number: 029103
Product name: Rai1-flox (Rai1^flox)
Research areas: Cancer Research, Cell Biology Research, Diabetes and Obesity Research, Neurobiology Research, Research Tools

Description

The Rai1^flox allele has loxP sites flanking exon 3 of the retinoic acid induced 1 gene. Removal of the floxed sequence creates a null allele. These mice may be useful in studying circuit assembly and neuronal communication in human disorders such as Smith-Magenis syndrome(SMS).

Detailed description

Haploinsufficiency of retinoic acid induced 1 (RAI1) in humans causes Smith-Magenis syndrome (SMS), which is associated with diverse neurodevelopmental and behavioral symptoms as well as obesity. RAI1 encodes a nuclear protein with emerging functions in the expression of genes involved in circuit assembly and neuronal communication.

The Rai1^flox allele has loxP sites flanking exon 3 of the retinoic acid induced 1 gene. Mice homozygous for this floxed allele are viable and fertile with no reported abnormalities. When bred to mice that express Cre recombinase, the resulting offspring will have the floxed region (encoding amino acid 1-1837) deleted in cre-expressing tissues; creating a knock-out allele (Rai1^Δ).

For example, when bred to mice with Cre-expression throughout the central and peripheral nervous system (Nestin-Cre; Stock No. 003771), the resulting Nestin^Cre;Rai1^CKO homozygotes have pan-neural loss of Rai1 and exhibit three major characteristics of SMS - deficits in body weight homeostasis, motor function and associative learning and memory. They are smaller than control littermates prior to weaning and show prominent hindlimb clasping. More than 80% die by 25 weeks of age. Females (but not males) show obesity beginning ~5 weeks of age.
Furthermore, individual aspects of these three major SMS phenotypes may be observed by crossing Rai1^flox to different cre-expressing mice.
Breeding to Gad2-IRES-Cre mice (Stock No. 010802) results in Rai1 knock-out in most GABAergic inhibitory neurons. Those Gad2^Cre;Rai1^CKO mice show learning deficits, but no motor function abnormalities, obesity or early lethality.
When bred to Vglut2-ires-cre mice (Stock No. 016963), the resulting Vglut2^Cre;Rai1^Tag mice have Rai1 knock-out in subcortical excitatory neurons - leading to increased body weight, poor motor function and learning deficits, with no early lethality. In addition, Rai1 knock-out specifically in neurons of the paraventricular nucleus of hypothalamus (PVH ; via breeding to Sim1-cre [see Stock No. 006395]) or ventromedial nucleus of hypothalamus (VMH ; via breeding to Sf1-Cre [Stock No. 012462]) both contributed to the obesity phenotype observed in Vglut2^Cre;Rai1^CKO mice.
No SMS-like characteristics were observed for mice with Rai1 knock-out in astrocytes and subsets of adult neural progenitors (via breeding to Gfap-Cre73.12 ; Stock No. 012886) or with Rai1 knock-out in cortical and hippocampal excitatory neurons and glia (via breeding to Emx1-IRES-Cre; Stock No. 005628).

Development

The Rai1^flox (floxed exon 3) allele was created by Dr. Liqun Luo (Stanford University). First, a targeting vector was designed to insert a frt5-flanked neo cassette (frt5-pSV40-Neo-pA-frt5) and a loxP site upstream of exon 3, and a loxP downstream of exon 3 of the retinoic acid induced 1 gene (Rai1) on chromosome 11. The targeting vector was electroporated into 129S1/Sv-derived embryonic stem (ES) cells. Chimeric males were mated with Flp-transgenic females (undisclosed genetic background) for germline deletion of the neo cassette. The resulting Rai1^flox mice were backcrossed to C57BL/6J wildtype mice for at least four generations (and the Flp-expressing transgene was removed) prior to sending males with black coat color to The Jackson Laboratory Repository in 2017. Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).
Of note, the donating investigator reports that, at least once during backcrossing, a heterozygous female was bred to a C57BL/6J inbred male (thus the Y chromosome of the congenic strain is of C57BL/6J origin).

Allele

Symbol: Rai1^tm2.1Luo
Name: targeted mutation 2.1, Liqun Luo
MGI accession ID: MGI:5816464
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed)
Synonyms: Rai1^flox; Rai1-flox
Marker symbol: Rai1
Marker name: retinoic acid induced 1
Marker synonyms: Gt1; SMCR; SMS
Chromosome: 11
Strain of origin: 129S1/Sv
Molecular note: A targeting vector was designed to insert a FRT5-flanked neo cassette (frt5-pSV40-Neo-pA-frt5) and a loxP site upstream of exon 3, and a loxP downstream of exon 3. Flp-mediated recombination removed the FRT5-flanked neo cassette.