Failure to replicate linkage between chromosome 5q11-q13 markers and schizophrenia in 28 families

Linkage and associated studies of schizophrenia

Genetic epidemiology has provided consistent evidence over many years that schizophrenia has a genetic component, and that this genetic component is complex, polygenic, and involves epistatic interaction between loci. Molecular genetics studies have, however, so far failed to identify any DNA variant that can be demonstrated to contribute to either liability to schizophrenia or to any identifiable part of the underlying pathology. Replication studies of positive findings have been difficult to interpret for a variety of reasons. First, few have reproduced the initial findings, which may be due either to random variation between two samples in the genetic inputs involved, or to a lack of power to replicate an effect at a given alpha level. Where positive data have been found in replication studies, the positioning of the locus has been unreliable, leading no closer to positional cloning of genes involved. However, an assessment of all the linkage studies performed over the past ten years does suggest a number of regions where positive results are found numerous times. These include regions on chromosomes 1, 2, 4, 5, 6, 7, 8, 9, 10, 13, 15, 18, 22 and the X. All of these data are critically reviewed and their locations compared. Reasons for the difficulty in obtaining consistent results and possible strategies for overcoming them are discussed. Am. J. Med. Genet. (Semin. Med. Genet.) 97:23-44, 2000.

Failure to support a pseudoautosomal locus for schizophrenia

Evidence for a pseudoautosomal locus for schizophrenia was sought through an assessment of the psychiatric status of the uncles and aunts (n = 30) of schizophrenic patients. The proportion of affected paternal uncles did not differ from that of affected paternal aunts. Likewise, the proportion of affected maternal aunts did not differ from that of affected maternal uncles. The research design used in this study failed to support the pseudoautosomal hypothesis of schizophrenia.

New directions in the prevention and treatment of schizophrenia: a biological perspective

Our current treatments for schizophrenia are, at best, palliative. With the exception of counseling those families with a known high risk for having schizophrenic offspring, no preventive measures are currently available. The not too distant future, however, promises to bring improvements in somatic treatments as well as the possible introduction of preventive measures. We are fully aware that current biological treatments work best when they are combined with psychosocial intervention, and expect that future biological treatments and preventions will also involve appropriate nonbiological considerations. Psychosocial treatments are covered elsewhere in this issue. Here we look at how modern genetics, pre- and perinatal factors, early and sustained intervention, and new medications are likely to decrease both the number of individuals with schizophrenia and the severity of the illness.

Pseudoautosomal region in schizophrenia: linkage analysis of seven loci by sib-pair and lod-score methods

In a previous study, we reported a nonrandom segregation between schizophrenia and the pseudoautosomal locus DXYS14 in a sample of 33 sibships. That study has been extended by the addition of 16 new sibships from 16 different families. Data from six other loci of the pseudoautosomal region and of the immediately adjacent part of the X specific region have also been analyzed. Two methods of linkage analysis were used: the affected sibling pair (ASP) method and the lod-score method. Lod-score analyses were performed on the basis of three different models--A, B, and C--all shown to be consistent with the epidemiological data on schizophrenia. No clear evidence for linkage was obtained with any of these models. However, whatever the genetic model and the disease classification, maximum lod scores were positive with most of the markers, with the highest scores generally being obtained for the DXYS14 locus. When the ASP method was used, the earlier finding of nonrandom segregation between schizophrenia and the DXYS14 locus was still supported in this larger data set, at an increased level of statistical significance. Findings of ASP analyses were not significant for the other loci. Thus, findings obtained from analyses using the ASP method, but not the lod-score method, were consistent with the pseudoautosomal hypothesis for schizophrenia.