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Galphas transcripts are biallelically expressed in the human kidney cortex: implications for pseudohypoparathyroidism
H Zheng1, G Radeva, J A McCann
1Department of Pediatrics, McGill University, Montréal, Québec, Canada H3Z 2Z3.
The Journal of Clinical Endocrinology and Metabolism
|October 16, 2001
Summary
Pseudohypoparathyroidism type 1b involves kidney resistance to parathyroid hormone (PTH). Studies suggest abnormal imprinting of GNAS1 locus regions, not just Galphas, causes this condition.
Area of Science:
- Endocrinology
- Genetics
- Molecular Biology
Background:
- Pseudohypoparathyroidism type 1b (PHP1b) presents with renal resistance to parathyroid hormone (PTH).
- Previous research suggested paternal imprinting of GNAS1 affecting Galphas in renal proximal tubules causes PHP1b.
- Albright's hereditary osteodystrophy and other endocrine issues are typically absent in PHP1b.
Purpose of the Study:
- To investigate the allelic expression of GNAS1 in human fetal kidney cortex.
- To determine if paternal imprinting of Galphas is the sole cause of PHP1b.
Main Methods:
- Analysis of GNAS1 allelic expression using RT-PCR in human fetal kidney cortex samples.
- Comparison of Galphas transcript expression with known imprinted transcripts (exon 1A, XLalphas, NESP).
Main Results:
- Galphas transcripts demonstrated biallelic expression in the human kidney cortex.
- This contrasts with the parent-specific (imprinted) expression of other GNAS1-related transcripts like exon 1A, XLalphas, and NESP.
Conclusions:
- Abnormal imprinting of alternative regions within the GNAS1 locus is implicated in PHP1b.
- The findings challenge the hypothesis of solely paternal imprinting of Galphas as the cause of PHP1b.