Reproductive endocrine phenotypes relating to CHD7 mutations in humans

Area of Science:

• Genetics and Developmental Biology
• Endocrinology
• Neuroscience

Background:

• CHARGE syndrome, caused by CHD7 gene mutations, frequently involves gonadal defects (60-80% of cases).
• These defects stem from congenital Gonadotropin-releasing hormone (GnRH) deficiency, causing hypogonadotropic hypogonadism and infertility.
• Additional endocrine issues like growth hormone deficiency can occur in a minority of patients.

Purpose of the Study:

• To investigate the role of CHD7 mutations in hypogonadotropic hypogonadism (HH).
• To explore the association between CHD7 mutations and Kallmann syndrome, including normosmic HH.
• To understand how CHD7 mutations impact GnRH neuron development and function.

Main Methods:

• Genetic analysis of individuals with Kallmann syndrome and normosmic HH.
• Functional studies of CHD7 missense mutations assessing ATPase and nucleosome remodeling activities.
• Review of existing literature on CHARGE syndrome and GnRH deficiency.

Main Results:

• Deleterious missense mutations in CHD7 are linked to Kallmann syndrome and normosmic HH.
• These mutations impair the ATPase and nucleosome remodeling functions of the CHD7 protein.
• CHD7 is critical for olfactory axon targeting and GnRH neuron migration during embryonic development.

Conclusions:

• CHD7 mutations disrupt GnRH neuron development, leading to hypogonadotropic hypogonadism and anosmia.
• The CHD7 protein is essential for the ontogeny of GnRH neurons and neuroendocrine control of reproduction.
• Understanding CHD7's role provides insights into the pathogenesis of Kallmann syndrome and related disorders.