Haplotype analysis improves molecular diagnostics of autosomal recessive polycystic kidney disease.
BACKGROUND
Autosomal recessive polycystic kidney disease (ARPKD) is characterized by wide phenotypic variability, ranging from in utero detection with enlarged, echogenic kidneys to an adult presentation with congenital hepatic fibrosis. The ARPKD gene, PKHD1 , covers about 470 kb of DNA (67 exons), and mutation studies have found marked allelic heterogeneity with a high level of novel missense changes and neutral polymorphisms. To improve the prospects for molecular diagnostics and to study the origin of some relatively common mutations, the authors have developed a strategy for improved ARPKD haplotyping.


METHODS
A protocol of multiplex PCR and fluorescence genotyping in a single capillary has been developed to assay 7 highly informative simple sequence repeat (SSR) markers that are intragenic or closely flanking PKHD1.


RESULTS
Examples in which haplotype analysis, used in combination with mutation screening, improved the utility of molecular diagnostics, especially in families in which just a single PKHD1 mutation has been identified, are illustrated. The new markers also allow screening for larger DNA deletions, detecting unknown consanguinity and exploring the disease mechanism. Analysis of 8 recurring mutations has shown likely common haplotypes for each, and the divergence from the ancestral haplotype, by recombination, can be used to trace the history of the mutation. The common mutation, T36M, was found to have a single European origin, about 1,225 years ago.


CONCLUSIONS
Improved haplotype analysis of ARPKD complements mutation-based diagnostics and helps trace the history of common PKHD1 mutations.
Consugar
Mark B
MB
Division of Nephrology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
Anderson
Sarah A
SA
Rossetti
Sandro
S
Pankratz
V Shane
VS
Ward
Christopher J
CJ
Torra
Roser
R
Coto
Eliecer
E
El-Youssef
Monif
M
Kantarci
Sibel
S
Utsch
Boris
B
Hildebrandt
Friedhelm
F
Sweeney
William E
WE
Avner
Ellis D
ED
Torres
Vicente E
VE
Cunningham
Julie M
JM
Harris
Peter C
PC
D024509:3' Flanking Region / Q000235:genetics; D024506:5' Flanking Region / Q000235:genetics; D000293:Adolescent; D000328:Adult; D002648:Child; D015331:Cohort Studies; D021901:DNA, Intergenic / Q000235:genetics; D005260:Female; D005819:Genetic Markers / Q000235:genetics; D005838:Genotype; D006239:Haplotypes / Q000235:genetics*; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D009154:Mutation / Q000235:genetics; D017044:Polycystic Kidney, Autosomal Recessive / Q000175:diagnosis* / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000379:methods; D011956:Receptors, Cell Surface / Q000235:genetics
D021901:DNA, Intergenic; D005819:Genetic Markers; C451750:PKHD1 protein, human; D011956:Receptors, Cell Surface