PUBLIC RELEASE DATE:

1-Jun-2014

Contact: Glenna Picton picton@bcm.edu 713-798-4710 Baylor College of Medicine

HOUSTON (June 1, 2014) Baylor College of Medicine scientists defined a previously unrecognized genetic cause for two types of birth defects found in newborn boys, described in a report published today in the journal Nature Medicine.

"Cryptorchidism and hypospadias are among the most common birth defects but the causes are usually unknown," said Dr. Dolores Lamb, director of the Center for Reproductive Medicine at Baylor, professor and vice chair for research of urology and molecular and cellular biology at Baylor and lead author of the report.

Cryptorchidism is characterized by the failure of descent of one or both testes into the scrotum during fetal development. In the adult man, the testes produce sperm and the male hormone, testosterone. Hypospadias is the abnormal placement of the opening of the urethra on the penis. Both birth defects are usually surgically repaired during infancy.

Cryptorchidism occurs in about 3 percent of full term male births. Similarly, the incidence of hypospadias is about 1 in 125 births.

Lamb and colleagues used a method of genome wide screening (essentially a molecular karyotype) called array comparative genomic hybridization to study children with these defects. The method looks specifically at changes in chromosomal regions that have undergone duplication or deletions too small to see under a microscope, termed copy number variations. These genomic changes can alter gene dosage (gene gains or losses) resulting in a change in cell function.

In its analysis, the team showed that the cause of these birth defects in a subset of children with these defects of testis and penile development resulted from a change in the number of copies of a gene, VAMP7.

"The birth defects were a result of microduplication on the X chromosome that altered estrogen receptor and androgen receptor action in ways not previously recognized," said Lamb.

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Study identifies new genetic cause of male reproductive birth defects

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