NEMO
- THE GENE THAT CAUSES INCONTINENTIA
PIGMENTI
The cause of Incontinentia Pigmenti has
been traced to a defective gene on the X chromosome called
NEMO. The NEMO gene is of less than average size, spanning
about 23 thousand base pairs. The NEMO gene produces a
protein that is essential for cells, and defects in it
result in IP. Males with cannot survive without a
functioning NEMO gene, and thus die in utero. In females, some cells have a normal
functioning NEMO gene (from the normal X chromosome) while
other cells have a defective NEMO gene. Currently, it is
thought that the symptoms of IP in females result from
cells with a defective NEMO gene in the affected tissue.
Now that the gene has been found, this view can be tested.
The normal function of NEMO is to allow cells to respond to
outside signals, such as growth factors. Follow this
link to read more technical information on
NEMO with links to references and DNA and protein
sequence.
In about 85% of families, the mutation in the NEMO gene
that results in IP is identical, even though the families
are unrelated. A portion of the NEMO gene is duplicated,
and these duplicated parts can result in deletions that
disrupt the NEMO gene's function. This is unusual in human
genetic disorders (most of the time, the mutations are
different in different families). The presence of a
frequent mutation, however, allows for easier testing (see
the testing page).
What is NEMO?
NEMO stands for NF kappa B essential modulator. The gene is also known as IKKgamma or IKBKG, which is its "official" gene name. It is involved in a cellular process known as "signal transduction" where signals from outside the cell are transmitted to the nucleus of the cell to alter gene expression.