AnkbL1622I/L1622I (Ank2) knock-in mice develop a metabolic syndrome characterized by early-onset pancreatic β cell dysfunction and age- or diet-dependent increases in adiposity and insulin resistance. Tissue-specific ANK2 deficiency is also observed.
Vann Bennett, Duke University Medical Center
Ankyrin-B (Ank2; AnkB) is a member of the ankyrin family of membrane adaptors that contributes to the assembly of diverse specialized plasma membrane domains. In humans, the p.L1622I variant, located in the unstructured C-terminal regulatory domain, is the most common ANK2 mutation in African Americans at over 7%, with a presence of less than 0.1% of individuals of mixed European decent. In humans, the mutation is involved with the setting of hereditary cardiac arrhythmia.
These knock-in mice carry the L1622I mutation in the Ank2 gene. Homozygotes develop a metabolic syndrome characterized by early-onset pancreatic β cell dysfunction and age- or diet-dependent increases in adiposity and insulin resistance. Tissue-specific ANK2 deficiency is also observed.
Homozygous mice are born at the expected Mendelian ratios and exhibit no differences in mRNA levels, as assessed by qPCR. Protein levels in homozygotes, however, are reduced significantly in a subset of tissues, including fat, liver, skeletal muscle, pancreatic β cells, and heart. Primary mouse embryonic fibroblast (MEF) cultures also show reduced protein expression. No change in protein expression is detected in the brain.
In contrast to Ank2R1788W/R1788W mutant animals (see Stock No. 027915), islets isolated from Ank2L1622I/L1622I mutant animals respond normally to glucose stimulation. Homozygous Ank2R1788W mutant mice exhibit over 50% reduction in glucose-stimulated insulin secretion (normalized to total insulin content).
While fasting serum glucose levels are unaltered in both Ank2R1788W and Ank2L1622I homozygous mice, oral administration of glucose (2 g/kg body weight) during an oral glucose tolerance test leads to both an increased level of blood glucose at 30 minutes as well as a delay in glucose clearance. The areas under the blood glucose response curves are significantly increased by 2- and 1.7 fold in homozygous Ank2R1788W and Ank2L1622I knock-in mice, respectively. Heterozygotes demonstrate 1.8- and 1.4-fold increases, respectively.
Both 3-month-old and 10-month-old Ank2R1788W and Ank2L1622I homozygous mice show overall similar average rates of food intake, energy source utilization, and activity compared with littermate controls during both light and dark cycles.
Both Ank2R1788W and Ank2L1622I homozygous mutant mice exhibit
significant adipocyte hypertrophy (54% increase in adipocyte diameter in Ank2R1788W and 38% in Ank2L1622I mice) which is accompanied by elevated levels of circulating nonesterified fatty acids. The increase in body fat is more prominent than the overall changes in total body weight.
It has not been determined whether mice carrying the Ank2L1622I mutation have a cardiac phenotype.
An L1622I (CTG to ATC) mutation in exon 19 and loxP-flanked neomycin cassette were knocked into the mouse Ank2 gene through homologous recombination in 129-derived embryonic stem cells. Resultant chimeric mice were bred with C57BL/6J animals. Although it was reported that the floxed neomycin cassette was excised though crosses with CMV-Cre mice (see Stock No. 006054), the neomycin cassette, segregating with the L1622I mutation, is still present.
A 32 SNP (single nucleotide polymorphism) panel analysis, with 27 markers covering all 19 chromosomes and the X chromosome, as well as 5 markers that distinguish between the C57BL/6J and C57BL/6N substrains, was performed on the rederived living colony at The Jackson Laboratory Repository. Three of the 27 markers throughout the genome were segregating, suggesting an incomplete backcross.
|Allele Name||ankyrin 2, brain; targeted mutation 2, Vann Bennett|
|Allele Type||Targeted (Humanized sequence)|
|Gene Symbol and Name||Ank2, ankyrin 2, brain|
|Strain of Origin||129|
|Molecular Note||An L1622I (CTG to ATC) mutation in exon 19 and loxP-flanked neomycin cassette were knocked into the gene. In humans, the mutation is involved with the setting of hereditary cardiac arrhythmia.|
Heterozygotes and homozygotes are viable and fertile.
When using the AnkbL1622I mouse strain in a publication, please cite the originating article(s) and include JAX stock #027914 in your Materials and Methods section.