Molecular basis of the Cd36 chromosomal deletion underlying SHR defects in insulin action and fatty acid metabolism

Abstract

The human insulin resistance syndromes---type 2 diabetes, obesity, combined hyperlipidemia, and essential hypertension---are genetically complex disorders whose molecular basis is largely unknown. The spontaneously hypertensive rate (SHR) is a model of these human syndromes. In the SHR/NCrlBR strain, a chromosomal deletion event that occurred at the Cd36 locus during the evolution of this SHR strain has been proposed as a cause of defective insulin action and fatty acid metabolism. In this study, three copies of the Cd36 gene, one transcribed copy and two pseudogenes, were identified in normal rat strains, but only a single gene in SHR/NCrlBR. Analysis of SHR genomic sequence localized the chromosomal deletion event between intron 4 of the normally transcribed copy of the gene and intron 4 of the second pseudogene. The deletion led to the creation of a single chimeric Cd36 gene in SHR/NCrlBR. The boundaries of the recombination/deletion junction identified within intron 4 were surrounded by long interspersed nuclear elements (LINEs) and DNA topoisomerase I recognition sequences. An 8-bp deletion at the intron 14/exon 15 boundary of the second pseudogene abolishes the putative splice acceptor site and is the cause of an aberrant 3' UTR previously observed in SHR/NCrlBR. We conclude that in SHR/NCrlBR, the complex trait of insulin resistance and defective fatty acid metabolism is caused by Cd36 deficiency, resulting from a chromosomal deletion caused by unequal recombination. This demonstrates that chromosomal deletions caused by unequal recombination can be a cause of quantitative or complex mammalian phenotypes.

Identification of Abcc6 as the major causal gene for dystrophic cardiac calcification in mice through integrative genomics

“…6), and several other inbred strains of mice resistant to DCC, including the A/J, MRL/MpJ, and BALB/cJ. The 3Ј-UTR can play an important role in translational control and mRNA stability, and mutations affecting the 3Ј-UTR have been shown to cause reduced level of transcript (14,15). To test the possibility of this 10-bp deletion as the causal mutation, we performed a GFP reporter assay for chimeric constructs expressing 3Ј-UTR of the B6 or C3H allele under the control of CMV promoter (SI Fig.…”

Retinoid X receptors: X-ploring their (patho)physiological functions

“…Deficient CD36 expression is a primary defect responsible for insulin resistance in spontaneously hypertensive rats (SHR), whereas transgenic rescue of CD36 can ameliorate insulin resistance in SHR. 159 Thus, upregulation of CD36 might also contribute to the insulin-sensitizing activity of rexinoids.…”

Uncovering the uncharacterized and unexpected: Unbiased phenotype‐driven screens in the mouse

“…For example, the oblivious mutant line was identified in the Beutler lab innate immunity screen because the animals are insensitive to specific immune stimuli and turned out to be a null allele of CD36 . While CD36 had previously been deleted from the germ line through homologous recombination, it had been linked to fatty acid uptake and recognition of oxidized LDL particles and not to immunity (Aitman et al, 1999;Glazier et al, 2002). The link between CD36 to TLRs found in the obl mutant was not appreciated in the analysis of the targeted CD36 mutant mice because of preconceived ideas about CD36 function.…”