Genetics of growth hormone gene expression

Area of Science:

• Endocrinology
• Molecular Biology
• Genetics

Background:

• Pituitary growth hormone (GH) gene expression is regulated by transcription factors binding to specific DNA sequences.
• The POU homeodomain protein Pit-1 is crucial for the differentiation and hormone production of somatotrophs, lactotrophs, and thyrotrophs.
• Defects in GH secretion can arise from mutations in the GH-1 promoter or the Pit-1 gene.

Purpose of the Study:

• To investigate the genetic basis of extreme growth failure in children.
• To identify mutations in the GH-1 and Pit-1 genes associated with pituitary hormone deficiencies.
• To understand the molecular mechanisms underlying GH deficiency and related endocrine disorders.

Main Methods:

• Genetic analysis of the GH-1 and Pit-1 genes in children with extreme growth failure.
• Examination of kindreds with combined GH, prolactin (Prl), and thyrotropin (TSH) deficiency.
• In vitro and in vivo studies to assess the functional impact of identified mutations.

Main Results:

• Various mutations in the Pit-1 gene were identified, including nonsense, missense, and dominant-negative mutations affecting transcriptional activation.
• Deletions in the GH-1 coding sequence, ranging from large deletions to small frameshifts, were observed.
• All identified mutations resulted in complete GH deficiency, with variable antibody development during treatment.

Conclusions:

• Mutations in the Pit-1 gene are a significant cause of combined GH, Prl, and TSH deficiency.
• GH-1 gene mutations lead to GH deficiency, with diverse clinical presentations.
• Understanding these genetic defects is crucial for diagnosing and managing pituitary hormone deficiencies and growth disorders.