Human diseases caused by homozygous PTH1R mutations

Area of Science:

• Endocrinology
• Skeletal Biology
• Genetics

Background:

• The parathyroid hormone receptor type 1 (PTH1R) is crucial for calcium homeostasis and skeletal development, mediating signals from parathyroid hormone (PTH) and PTH-related protein (PTHrP).
• Loss-of-function mutations in PTH1R can lead to severe developmental disorders, such as Blomstrand's lethal chondrodysplasia, characterized by accelerated growth plate ossification.

Purpose of the Study:

• To investigate the spectrum of clinical phenotypes associated with PTH1R mutations.
• To understand the functional consequences of various PTH1R mutations, including those in transmembrane helices, extracellular domains, and the C-tail.
• To explore the relationship between specific PTH1R mutations and the resulting skeletal and mineral abnormalities.

Main Methods:

• Analysis of patient genetic data to identify PTH1R mutations.
• Clinical evaluation of patients with identified PTH1R mutations, focusing on skeletal and mineral abnormalities.
• Pharmacologic characterization of mutant PTH1R proteins to assess their function.

Main Results:

• Homozygous mutations in PTH1R cause lethal chondrodysplasia with accelerated ossification.
• Milder skeletal and mineral abnormalities, including Eiken syndrome (delayed ossification) and hypocalcemia, result from homozygous mutations in specific PTH1R domains.
• Heterozygous PTH1R mutations are often linked to primary failure of tooth eruption.

Conclusions:

• PTH1R mutations represent a significant genetic cause of diverse skeletal dysplasias and mineral imbalances.
• The location and type of PTH1R mutation correlate with the severity and specific phenotype of the disorder.
• Detailed functional studies of PTH1R mutants are essential for understanding disease mechanisms and potential therapeutic targets.