Requirement for the L-type Ca2+ channel α1D subunit in postnatal pancreatic β cell generation
Yoon Namkung, … , Sung-Sook Kim, Hee-Sup Shin
Yoon Namkung, … , Sung-Sook Kim, Hee-Sup Shin
Published October 1, 2001
Citation Information: J Clin Invest. 2001;108(7):1015-1022. https://doi.org/10.1172/JCI13310.
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Article

Requirement for the L-type Ca2+ channel α1D subunit in postnatal pancreatic β cell generation

Abstract

Pancreatic β cells are the source of insulin, which directly lowers blood glucose levels in the body. Our analyses of α1D gene-knockout (α1D–/–) mice show that the L-type calcium channel, α1D, is required for proper β cell generation in the postnatal pancreas. Knockout mice were characteristically slightly smaller than their littermates and exhibited hypoinsulinemia and glucose intolerance. However, isolated α1D–/– islets persisted in glucose sensing and insulin secretion, with compensatory overexpression of another L-type channel gene, α1C. Histologically, newborn α1D–/– mice had an equivalent number of islets to wild-type mice. In contrast, adult α1D–/– mice showed a decrease in the number and size of islets, compared with littermate wild-type mice due to a decrease in β cell generation. TUNEL staining showed that there was no increase in cell death in α1D–/– islets, and a 5-bromo-2′ deoxyuridine-labeling (BrdU-labeling) assay illustrated significant reduction in the proliferation rate of β cells in α1D–/– islets.

Authors

Yoon Namkung, Nataliya Skrypnyk, Myung-Jin Jeong, Taehoon Lee, Myung-Shik Lee, Hyung-Lae Kim, Hemin Chin, Pann-Ghill Suh, Sung-Sook Kim, Hee-Sup Shin

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Figure 1

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Targeted disruption of the calcium channel α1D gene by homologous recomb...
Targeted disruption of the calcium channel α1D gene by homologous recombination. (a) A diagram of α1D cDNA with the four transmembrane domains and structures of the wild-type locus, targeting vector, and targeted locus are shown. Restriction enzymes: B, BamHI; X, XbaI; K, KpnI. Solid boxes indicate exons. Hatched boxes underneath the wild-type and targeted locus signify the probe used for Southern blotting. IRES-βgal-pA was used for staining but, for unknown reasons, was not detectable in the mutant. NEO, neomycin-resistance gene with the PGK promoter. TK, thymidine kinase with the PGK promoter. (b) Genomic Southern blot on offspring from the heterozygote matings. The 6.2-kb band is the wild-type allele and the 4.5-kb band is the targeted allele. (c) Western blot of cerebral membrane fractions from wild-type and α1D–/– mice. Mr markers in kDa are indicated on the left. The mAb (α1D 185-1) against the α1D peptide (RNKNSDKQRSA, corresponding to residues 2048–2058 of human α1D) specifically recognized a protein with a molecular weight of approximately 220 kDa from wild-type brain that was lacking in the mutant.