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19p13.2 microdeletions - Unique The Rare Chromosome Disorder ...

19p13.2 microdeletions - Unique The Rare Chromosome Disorder ...

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One 16 year old girl started menstruating at aged 11 years. Another female, of unknown<br />

age, has secondary amenorrhea; this occurs when a woman who has been having normal<br />

menstrual cycles stops getting her periods for six or more months. A 16-year-old boy has<br />

low testosterone and is on testosterone injections to correct this imbalance (Decipher,<br />

<strong>Unique</strong>).<br />

Ongoing research involving <strong>19p13.2</strong><br />

<strong>The</strong> <strong>19p13.2</strong> region is located between 6.9Mb and 12.6 Mb on chromosome 19 (see<br />

diagram). <strong>The</strong> variation in size of the <strong>microdeletions</strong> (0.18Mb – 3.42Mb) within this region<br />

can mean anything from 7- 96 genes can be missing (see diagram below). Candidate<br />

genes that might play a part in the features associated with <strong>19p13.2</strong> microdeletion<br />

include:<br />

Insulin receptor and resistin: genes that could predispose to obesity as they regulate<br />

glucose (sugar) metabolism.<br />

PDE4A – an enzyme that has been linked to conditions that affect the brain such as:<br />

Alzheimer’s, Parkinson’s, bipolar disorder, mild learning disabilities, autism and<br />

depression.<br />

S1RPF, CDKN2D and AP1M2 – involved in the development of the brain<br />

(Haberlandt 2012, Wangensteen 2013)<br />

6,900 000<br />

7,000,000<br />

Some genes (and their base<br />

pair position) located on <strong>19p13.2</strong>:<br />

8,000,000<br />

9,000,000<br />

10,000,000<br />

11,000,000<br />

PDE4A (10,430,645-10,441,307)<br />

CDKN2D (10,538,138-10,540,655)<br />

AP1M2 (10,544,347-10,558,991)<br />

<strong>Chromosome</strong> 19<br />

12,000,000<br />

12,600,000<br />

As this is a gene-dense region, there are likely to be a number of different genes<br />

involved; the precise size and location of the deletion (see diagram) will govern which<br />

genes are deleted. It is also important to remember that, while identifying the gene(s)<br />

responsible for certain features of <strong>19p13.2</strong> microdeletion is valuable and may help guide<br />

future studies, it does not lead directly to immediate improved treatment. In addition,<br />

even if a gene is missing it does not always mean that the associated feature(s) will be<br />

evident or that there is a direct relationship between an absent gene and a particular<br />

feature. Other genetic and environmental factors often have a role in determining the<br />

presence or absence of a particular feature.<br />

25

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