PROKR2 mutations in autosomal recessive Kallmann syndrome

Area of Science:

• Genetics and Molecular Biology
• Endocrinology
• Reproductive Medicine

Background:

• Kallmann syndrome, characterized by hypogonadotropic hypogonadism and anosmia, can result from genetic defects in the GnRH pathway.
• The PROKR2 gene and its ligand PROK2 are implicated in the development of the olfactory system and reproductive axis.

Observation:

• A family with two brothers affected by congenital hypogonadotropic hypogonadism and anosmia (Kallmann syndrome) was studied.
• Both affected brothers were homozygous for two PROKR2 variants: a novel mutation (p.G234D) and a known polymorphism (p.R268C).

Findings:

• The affected brothers presented with homozygous PROKR2 variants, while their heterozygous parents were fertile, supporting a recessive inheritance pattern.
• Treatment with recombinant human FSH in the proband led to a significant increase in serum inhibin B levels.
• PROKR2 signaling does not appear to directly influence Sertoli cell function.

Implications:

• This research clarifies the role of PROKR2 in the etiology of Kallmann syndrome, highlighting a recessive mode of inheritance for specific variants.
• Understanding the genetic basis of Kallmann syndrome is crucial for diagnosis and potential therapeutic strategies.
• The findings contribute to the broader understanding of reproductive endocrinology and the genetic factors influencing male fertility.