New technique determines which patients with homocystinuria are most likely to respond to vitamin B6 treatment based on their genotypes

Although the current study focused on homocystinuria, testing the effects of naturally occurring gene variations using surrogate organism genetics can be applied to other inherited disorders, such as neural tube defect, cleft palate, and blindness.

"The era of personal genome sequences is upon us, but there is a growing gap between the ability to sequence human genomes and the ability to understand the significance of variation in genome sequences," said Jasper Rine, Ph.D., the principal investigator of this research in the Department of Molecular and Cell Biology at the California Institute of Quantitative Biosciences at the University of California, Berkeley. "This study demonstrates one way to close the gap; the data separate gene variants into distinct classes, including a group amenable to dietary intervention."

To make their determination, scientists "swapped" the cystathionine beta synthase gene of baker's yeast with the gene from humans to test which variants were healthy, treatable, or untreatable with additional vitamin B6. As a result, the study clarified the function of 84 DNA sequence variants in this gene, which will help physicians more effectively treat patients based on their particular genotypes. In addition, this approach opens doors for future studies examining other human genes that similarly cross over between humans and yeast.

"We may have the DNA sequence of the human genome, but we're still trying to figure out what it means," said Mark Johnston, Editor-in-Chief of the journal Genetics. "This study moves us a step closer toward better understanding the genetic variability among people. More immediately, knowledge of these gene mutations will help physicians prescribe treatment based on genotype rather than outward symptoms or trial and error."