Mice lacking the Ink4d gene become progressively hearing impaired because the absence of Ink4d causes certain cells in their inner ears to attempt to divide. However, this inappropriate attempt to divide causes these cells, called sensory hair cells, to instead commit suicide, according to a team of researchers that includes two St. Jude investigators and scientists from the House Ear Institute in Los Angeles, CA.

This finding in mice represents a potentially unrecognized form of progressive hearing loss, a problem that also occurs in humans, according to the investigators. If problems in Ink4d also occur in humans, this finding could explain the slow development of deafness in some people. In the absence of the braking effect of normally functioning Ink4d genes, sensory hair cells in people's ears might attempt to divide, setting off a biological response called apoptosis, or programmed cell death.

This observation in mice suggests that a person who lacks one or both copies of Ink4d, or who has Ink4d genes that are not very active, might suffer progressive hair cell death and experience hearing loss, just as mice do, according to Neil Segil, Ph.D., a researcher at the House Ear Institute and a research associate professor at the University of Southern California Medical School (Los Angeles). Segil, a senior author of a paper reporting these results, published in the May 2003 issue of Nature Cell Biology, speculates that the lack of one or both Ink4d genes makes the person more susceptible to hair cell loss from a variety of different traumas, such as loud noise or certain medicines. According to this theory, trauma could stimulate hair cel
'"/>

Contact: Bonnie Cameron
bonnie.cameron@stjude.org
901-495-4815
St. Jude Children's Research Hospital
1-May-2003