Fróðskaparrit - 01.01.1998, Page 8

14
HUMAN POPULATION GENETICS IN THE FAROEISLANDS
Etiological heterogenity which makes
mapping of disease genes difficult is very
likely in bipolar affective disorder. In the
present study several measures were taken
in order to identify an apparently homoge-
nous subform of bipolar disorder. Cases re-
lated around six generations ago whose an-
cestors originated from a certain regions of
the Faroe Islands were selected. Furtermore
only cases responding to lithium treatment
as defined by Grof et al. (1994) were col-
lected.
Though both parents were alive for only
two out of the eight patients only in a few
instances were the haplotype not inferable
due to the patient and parent being of iden-
tical genotype. Thus, in reality, the search
for a common haplotype may not be great-
ly impeded even when only one of the par-
ents are available.
We will collect a representative sample
of around 100 persons from the relevant re-
gions of the Faroe Islands in order to eval-
uate the allele frequency in the background
population. This may also allow significant
allele sharing between a fraction of the af-
fected persons to be detected.
The present study reports preliminary re-
sults from chromosomes 16 and 18. Con-
ceming chromosome 16 the most distal
marker on chromosome 16p showed evi-
dence of increased marker allele sharing,
which is interesting as we earlier have
found possible evidence of linkeage to
chromosome 16pl3.3 with a maximum
FOD score of 2.76 for D16S510 which is
located around 3 cM proximal to
D16S2622. However, as the distance to the
marker proximal to D16S2622 is 14 cM ad-
ditional testing of markers in this region is
necessary.
Concerning interesting markers on chro-
mosome 18, 13 out of 16 alleles were sha-
red for marker D18S541. This marker is lo-
cated distal on chromosome 18q, proximal
in the area in which Freimer et al. (1996)
found evidence of haplotype sharing in
Costa Rica. More markers will be tested in
that area in the near future. D18S877 is lo-
cated on chromosome 18q 12, i.e. in the
pericentrometric region. Earlier reports
have been about positive LOD scores at this
marker (1.56 for a narrow phenotypic mo-
del) in a large family (Ewald et al. 1995).
Some evidence of increased allele sharing
were also found at marker D18S976 locat-
ed close to D18S62. As the neighbouring
markers were located 18 and 16 cM away
additional markers will be tested in that
area. The marker D18S542 which is the
marker closest to the perhaps most interest-
ing marker in the study by Berrettini et al.
(1994) and Stineetal. (1995). D18S37 also
showed some evidence of increased sharing
and additional markers will be tested in the
near future in that area.
The present study is part of a larger pro-
ject (FAROGENE) investigating several
different psychiatric diseases in the Faroe
Islands, including subtypes of affective dis-
order.
Acknowledgements
The project has been supported with grants from: Dan-
ish hospital foundation for medical research, region of
Copenhagen, the Faroe Islands and Greenland; The
Danish research counsils; Research fund of Føroya
Sparikassi; Ministry of Education, cuiture and research,
the Faroese Govemment.