Age-related maculopathy (ARM), or age-related macular degeneration, is one of the most common causes of visual impairment in the elderly population of developed nations. In a combined analysis of two previous genomewide scans that included 391 families, containing up to 452 affected sib pairs, we found linkage evidence in four regions: 1q31, 9p13, 10q26, and 17q25. We now have added a third set of families and have performed an integrated analysis incorporating 530 families and up to 736 affected sib pairs. Under three diagnostic models, we have conducted linkage analyses using parametric (heterogeneity LOD [HLOD] scores under an autosomal dominant model) and nonparametric (Sall statistic) methods. There is ongoing evidence of susceptibility loci within the 1q31, 10q26, and 17q25 regions. If we treat the third set of families as a replication set, then two regions (10q26 and 17q25) are replicated, with LOD scores >1.0. If we pool all our data together, then four regions (1q31, 2q14.3, 10q26, and 17q25) show HLOD or Sall scores > or =2.0. Within the 1q31 region, we observed an HLOD of 2.72 (genomewide P=.061) under our least stringent diagnostic model, whereas the 17q25 region contained a maximal HLOD of 3.53 (genomewide P=.007) under our intermediate diagnostic model. We have evaluated our results with respect to the findings from several new independent genomewide linkage studies and also have completed ordered subset analyses (OSAs) with apolipoprotein E alleles, smoking history, and age at onset as stratifying covariates. The OSAs generate the interesting hypothesis that the effect of smoking on the risk of ARM is accentuated by a gene in the 10q26 region--a region implicated by four other studies.
Age-related macular degeneration or age-related maculopathy (ARM) is a major public health issue, as it is the leading cause of irreversible vision loss in the elderly in the Western world. Using three diagnostic models, we have genotyped markers in 16 plausible candidate regions and have carried out a genome-wide screen for ARM susceptibility loci. A panel of 225 ARM families comprising up to 212 affected sib pairs was genotyped for 386 markers. Under our most stringent diagnostic model, the regions with the strongest evidence of linkage were on chromosome 9 near D9S301 and on 10 near D10S1230, with peak multipoint heterogeneity LOD scores (HLOD) of 1.87 and 1. 42 and peak GeneHunter-Plus non-parametric LOD scores (GHP LOD) of 1. 69 and 1.83. After expanding our initial set of families to 364 ARM families with up to 329 affected sib pairs, the linkage signal on chromosome 9 vanished, while the chromosome 10 signal decreased to a GHP LOD of about 1.0, with a SimIBD P -value of 0.008 under the broadest diagnostic model with marker D10S1236. After error filtration, the GHP LOD increased to 1.27 under our most stringent model and 1.42 under our broadest model, peaking near D10S1236. This peak was seen consistently across all three diagnostic models. Our analyses also excluded up to nine different candidate regions and identified a few other regions of potential linkage, suitable for further studies. Of particular interest was the region on chromosome 5 near D5S1480, where a reasonable candidate gene, glutathione peroxidase 3, resides.
The etiology of strabismus has long been observed to have a genetic component. Recent advances in genetic methodology may provide insight into the genetic basis for several types of inherited strabismus, including those associated with genetic multisystem disorders such as Moebius syndrome, Prader-Willi syndrome, craniofacial dysostoses, and mitochondrial myopathies. Inheritance of primary forms of strabismus, such as congenital ocular fibrosis, Brown syndrome and Duane syndrome, has been reported, but less is known of the defective genetic sites. The genetic basis for isolated strabismus that clusters in families, such as infantile esotropia syndrome, is also not yet known, but new techniques of molecular biology may now permit linkage detection in these families. By identifying affected families, clinicians will take part in unraveling the genetic basis of hereditary strabismus syndromes.
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