Genetic screening protocol for familial hypercholesterolemia which includes splicing defects gives an improved mutation detection rate.
Familial hypercholesterolemia (FH) is a common single gene disorder, which predisposes to coronary artery disease. In a previous study, we have shown that in patients with definite FH around 20% had no identifiable gene defect after screening the entire exon coding area of the low density lipoprotein receptor (LDLR) and testing for the common Apolipoprotein B (ApoB) R3500Q mutation. In this study, we have extended the screen to additional families and have included the non-coding intron splice regions of the gene. In families with definite FH (tendon xanthoma present, n=68) the improved genetic screening protocol increased the detection rate of mutations to 87%. This high detection rate greatly enhances the potential value of this test as part of a clinical screening program for FH. In contrast, the use of a limited screen in patients with possible FH (n=130) resulted in a detection rate of 26%, but this is still of significant benefit in diagnosis of this genetic condition. We have also shown that 14% of LDLR defects are due to splice site mutations and that the most frequent splice mutation in our series (c.1845+11 c>g) is expressed at the RNA level. In addition, DNA samples from the patients in whom no LDLR or ApoB gene mutations were found, were sequenced for the NARC-1 gene. No mutations were identified which suggests that the role of NARC-1 in causing FH is minor. In a small proportion of families (<10%) the genetic cause of the high cholesterol remains unknown, and other genes are still to be identified that could cause the clinical phenotype FH.
Graham
Colin A
CA
Regional Genetics Centre, Belfast City Hospital, Belfast BT9 7AB, Northern Ireland, UK. colin.graham@bll.n-i.nhs.uk
McIlhatton
Brian P
BP
Kirk
Claire W
CW
Beattie
E Diane
ED
Lyttle
Kelly
K
Hart
Padraig
P
Neely
R Dermot G
RD
Young
Ian S
IS
Nicholls
D Paul
DP
D001055:Apolipoproteins B / Q000235:genetics; D001483:Base Sequence; D005091:Exons / Q000235:genetics; D005820:Genetic Testing / Q000379:methods*; D006801:Humans; D006938:Hyperlipoproteinemia Type II / Q000175:diagnosis / Q000235:genetics*; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D022821:RNA Splice Sites / Q000235:genetics*; D011973:Receptors, LDL / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
D001055:Apolipoproteins B; D022821:RNA Splice Sites; D011973:Receptors, LDL