Rapid identification of mutations in GJC2 in primary lymphoedema using whole exome sequencing combined with linkage analysis with delineation of the phenotype.
BACKGROUND
Primary lymphoedema describes a chronic, frequently progressive, failure of lymphatic drainage. This disorder is frequently genetic in origin, and a multigenerational family in which eight individuals developed postnatal lymphoedema of all four limbs was ascertained from the joint Lymphoedema/Genetic clinic at St George's Hospital.


METHODS
Linkage analysis was used to determine a locus, and exome sequencing was employed to look for causative variants.


RESULTS
Linkage analysis revealed cosegregation of a 16.1 Mb haplotype on chromosome 1q42 that contained 173 known or predicted genes. Whole exome sequencing in a single affected individual was undertaken, and the search for the causative variant was focused to within the linkage interval. This approach revealed two novel non-synonymous single nucleotide substitutions within the chromosome 1 locus, in NVL and GJC2. NVL and GJC2 were sequenced in an additional cohort of individuals with a similar phenotype and non-synonymous variants were found in GJC2 in four additional families.


CONCLUSIONS
This report demonstrates the power of exome sequencing efficiently applied to a traditional positional cloning pipeline in disease gene discovery, and suggests that the phenotype produced by GJC2 mutations is predominantly one of 4 limb lymphoedema.
Medical Genetics, St George's, University of London, and Guy's Hospital, London SW17 ORE, UK.
Pia
P
Ostergaard
Michael A
MA
Simpson
Glen
G
Brice
Sahar
S
Mansour
Fiona C
FC
Connell
Alexandros
A
Onoufriadis
Anne H
AH
Child
Jae
J
Hwang
Kamini
K
Kalidas
Peter S
PS
Mortimer
Richard
R
Trembath
Steve
S
Jeffery
D017630:Connexins / Q000235:genetics*; D005260:Female; D008040:Genetic Linkage; D006801:Humans; D008206:Lymphatic Diseases / Q000235:genetics*; D008297:Male; D009154:Mutation; D010375:Pedigree; D010641:Phenotype; D017422:Sequence Analysis, DNA
D017630:Connexins; C427305:connexin 47