The Arntl knock-out strain may be useful in studies of circadian rhythm, arthritis, ankylosis, and glucose homeostasis.
Dr. Joseph S. Takahashi, Univ Texas Southwestern Medical Ctr
These targeted mutation mice exhibit a loss of both behavioral and molecular circadian rhythms. When placed in constant darkness, the mice undergo an immediate loss of circadian rhythmicity. Locomotor activity is impaired in both light and constant dark cycles.
Reduced total activity is seen as the mice age. They display a progressive noninflammatory arthropathy. Little pathology is seen prior to 11 weeks of age, but virtually all homozygotes develop joint ankylosis due to flowing ossification of ligaments and tendons by 35 weeks of age. Bone density and articular cartilage are unaffected.
Inactivation of the gene suppresses diurnal variation in glucose and triglycerides. Gluconeogenesis is abolished in homozygotes, but the counterregulatory response of corticosterone and glucagon to insulin-induced hypoglycemia is retained.
Homozygotes are viable but not fertile and have an increased mortality rate after 26 weeks of age. A truncated, non-functional protein is produced. This strain may be useful in studies of circadian rhythm, arthritis, ankylosis, and glucose homeostasis.
The helix-loop-helix domain within exon 4 and all of exon 5 were replaced with a neomycin resistance gene cassette. 129/Sv-derived GS1 embryonic stem (ES) cells were used to create the mutation. The donating investigator backcrossed this line 14 generation to C57BL/6, and then sent heterozygous males to the Jackson Laboratory in 2009. Upon arrival, males were used to cryopreserve sperm. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).
In 2020, it was discovered that the mice sent to The Jackson Laboratory in 2009 may have been segregating for an unreported, recessive albino allele that may still be segregating in our live colony (see details below). We will backcross our colony to C57BL/6J inbred mice for two or more generations in an attempt to delete the unknown albino allele.
Routine yearly SNP (single nucleotide polymorphism) panel testing was implemented for the living colony at The Jackson Laboratory beginning 2012. From 2012-2017, the tested cohorts all showed C57BL/6J allele-type.
In 2018, an expanded SNP panel analysis (48 markers) was implemented having 43 markers covering all 19 chromosomes and the X chromosome, as well as 5 markers that distinguish between the C57BL/6J and C57BL/6N substrains. Our living colony showed all 43 markers throughout the genome were C57BL/6 allele-type, including the marker within the Tyr locus on chromosome 7 (approximately 26 Mbp away from the targeted Arntl locus) that determines Tyr wildtype from Tyrc-2J. In addition, all 5 markers that determine C57BL/6J from C57BL/6N were found to be C57BL/6J allele-type.
In October 2019, the colony was re-established by using the cryopreserved sperm (frozen on arrival in 2009) to fertilize C57BL/6J oocytes. A cohort of the resulting first generation rederived mice were analyzed with the 48 SNP panel. This showed the same results as in 2018 - all 48 markers were C57BL/6J allele-type. Despite this, one of our breeding units of rederived mice (heterozygous female x wildtype male) produced some albino offspring in 2020 (the breeding unit was then discontinued). This suggests that the mice sent to The Jackson Laboratory in 2009 may have been segregating for an unreported, recessive albino allele and it may still be segregating in our live colony. We will backcross our colony to C57BL/6J inbred mice for two or more generations in an attempt to delete the unknown albino allele.
|Allele Name||targeted mutation 1, Christopher A Bradfield|
|Allele Type||Targeted (Null/Knockout)|
|Allele Synonym(s)||bmal1-; Bmal1-KO; mMop3-; Mop3-|
|Gene Symbol and Name||Arntl, aryl hydrocarbon receptor nuclear translocator-like|
|Strain of Origin||129/Sv|
|Molecular Note||A portion of exon 4 containing the helix-loop-helix coding domain and all of exon 5 were replaced by a neomycin selection cassette. A larger transcript, resulting from a cryptic splice site between exon 3 and the neomycin resistance gene, was detected by Northern blot analysis. The polypeptide truncates 15 residues after this splice site, prior to the functional domains encoded by exon 4 in the wild-type locus.|
|Mutations Made By|| |
Christopher Bradfield, University of Wisconsin-Madison
When maintained as a live colony, hetetozygotes may be bred. It is recommended that females be disturbed as little as possible because they are prone to killing their litters. Homozygotes are viable, but both males and females are reportedly sterile.
When using the Mop3- mouse strain in a publication, please cite the originating article(s) and include JAX stock #009100 in your Materials and Methods section.
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