SNP haplotype mapping in a small ALS family

Area of Science:

• Genetics
• Genomics
• Molecular Biology

Background:

• Identifying genes for monogenic disorders is crucial for understanding human disease mechanisms.
• A trend away from studying single-gene disorders exists due to challenges in mapping small families.
• New tools are needed to effectively map remaining single-gene disorders.

Purpose of the Study:

• To experimentally validate the use of high-density single nucleotide polymorphism (SNP) arrays and haploid cell lines for defining genome-wide haplotypes.
• To assess the accuracy of SNP arrays in predicting chromosomal haplotypes.
• To demonstrate the utility of these methods for mapping single-gene disorders in small families, using amyotrophic lateral sclerosis (ALS) as a prototype.

Main Methods:

• Generation of haploid cell line panels.
• Performing a 5 centimorgan (cM) short tandem repeat polymorphism (STRP) genome scan.
• Experimental determination of haplotypes for entire chromosomes.
• Comparison of experimentally derived haplotypes with in silico haplotypes predicted from SNP arrays using diploid DNA.

Main Results:

• High-density SNP arrays accurately predict chromosomal haplotypes.
• Haplotype information significantly enhances genetic analysis in small families.
• The methods precisely identified 12 candidate intervals shared by all 5 affected individuals in the ALS family.

Conclusions:

• Readily available tools, including SNP arrays and haploid cell lines, can maximize genetic information for mapping single-gene disorders.
• This approach provides a valuable first step for genetic mapping in small families.
• The validated methods offer a powerful strategy to overcome limitations in studying previously unmapped Mendelian disorders.