Haplotype and Multipoint Linkage Analysis in Finnish Choroideremia
Families
E-M. Sankila, T. Lehner, A.W. Eriksson, H. Forsius, J. Karna,
D. Page, J. Ott, A. de la Chapelle
Human Genetics , 84(1),66--70 (1989 Dec)
Abstract
Multipoint linkage analysis of choroideremia (TCD) and seven X
chromosomal restriction fragment length polymorphisms (RFLPs) was
carried out in 18 Finnish TCD families. The data place TCD distal to
PGK and DXS72, very close to DXYS1 and DXYS5 (Zmax = 24 at theta =
0) and proximal to DXYS4 and DXYS12. This agrees with the data
obtained from other linkage studies and from physical mapping. All
the TCD males and carrier females studied have the same DXYS1 allele
in coupling with TCD. In Northeastern Finland, 66/69 chromosomes
carrying TCD had the same haplotype at loci DXS72, DXYS1, DXYS4, and
DXYS12. The same haplotype is seen in only 15/99 chromosomes not
carrying TCD. Moreover, in 71/104 non-TCD chromosomes, the haplotype
at six marker loci is different from those seen in any of the 76 TCD
chromosomes. This supports the previously described hypothesis that
the large Northern Finnish choroideremia pedigrees, comprising a
total of over 80 living patients representing more than a fifth of
all TCD patients described worldwide, carry the same mutation. These
linkage and haplotype data provide improved opportunities for
prenatal diagnosis based on RFLP studies.
