This spontaneous mutation presents as a 4 base pair deletion in exon 21 at chromosome 16 position 10,694,632-635 bp (GRCm38), which results in a frameshift mutation that leads to the introduction of novel amino acids and an early termination codon. Transcript levels of this mutant allele were found to be significantly decreased in homozygous embryonic fibroblasts. (J:190968, J:222308, J:251104)