PROK2

Kallmann syndrome

At least 16 mutations in the PROK2 gene have been identified in people with Kallmann syndrome, a disorder characterized by the combination of hypogonadotropic hypogonadism (a condition affecting the production of hormones that direct sexual development) and an impaired sense of smell. Researchers estimate that mutations in the PROK2 and PROKR2 genes together account for about 9 percent of all cases of Kallmann syndrome.

Most of the PROK2 gene mutations that cause Kallmann syndrome change single protein building blocks (amino acids) in prokineticin 2. These mutations disrupt the protein's activity, affecting its ability to bind to its receptor to send signals normally. Studies suggest that a loss of this signaling disrupts the migration and survival of olfactory neurons and GnRH-producing neurons in the developing brain. If olfactory nerve cells do not extend to the olfactory bulb, a person's sense of smell will be impaired or absent. Misplacement or premature loss of GnRH-producing neurons prevents the production of sex hormones, which interferes with normal sexual development and causes puberty to be delayed or absent.

Because the features and severity of Kallmann syndrome vary among individuals, researchers believe that additional genetic and environmental factors may be involved. Some affected individuals have mutations in one of several other genes in addition to PROK2, and these genetic changes may contribute to the varied features of the condition.