Genetic ablation of parathyroid glands reveals another source of parathyroid hormone.
The parathyroid glands are the only known source of circulating parathyroid hormone (PTH), which initiates an endocrine cascade that regulates serum calcium concentration. Glial cells missing2 (Gcm2), a mouse homologue of Drosophila Gcm, is the only transcription factor whose expression is restricted to the parathyroid glands. Here we show that Gcm2-deficient mice lack parathyroid glands and exhibit a biological hypoparathyroidism, identifying Gcm2 as a master regulatory gene of parathyroid gland development. Unlike PTH receptor-deficient mice, however, Gcm2-deficient mice are viable and fertile, and have only a mildly abnormal bone phenotype. Despite their lack of parathyroid glands, Gcm2-deficient mice have PTH serum levels identical to those of wild-type mice, as do parathyroidectomized wild-type animals. Expression and ablation studies identified the thymus, where Gcm1, another Gcm homologue, is expressed, as the additional, downregulatable source of PTH. Thus, Gcm2 deletion uncovers an auxiliary mechanism for the regulation of calcium homeostasis in the absence of parathyroid glands. We propose that this backup mechanism may be a general feature of endocrine regulation.
Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA.
T
T
Günther
Z F
ZF
Chen
J
J
Kim
M
M
Priemel
J M
JM
Rueger
M
M
Amling
J M
JM
Moseley
T J
TJ
Martin
D J
DJ
Anderson
G
G
Karsenty
D000818:Animals; D001842:Bone and Bones / Q000378:metabolism / Q000473:pathology; D002118:Calcium / Q000378:metabolism; D003433:Crosses, Genetic; D004268:DNA-Binding Proteins; D017353:Gene Deletion; D018507:Gene Expression Regulation, Developmental; D018390:Gene Targeting; D051379:Mice; D008810:Mice, Inbred C57BL; D009479:Neuropeptides / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D010280:Parathyroid Glands / Q000002:abnormalities / Q000196:embryology / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000096:biosynthesis* / Q000097:blood; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013234:Stem Cells; D013950:Thymus Gland / Q000378:metabolism; D015534:Trans-Activators / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors
D004268:DNA-Binding Proteins; C101631:Gcm1 protein, mouse; D009479:Neuropeptides; D010281:Parathyroid Hormone; D015534:Trans-Activators; D014157:Transcription Factors; D002118:Calcium