SBDS Gene

From the Shwachman-Diamond Syndrome Newsletter, Summer 2003

One of the most important findings since the Verona meeting was the identification of the gene for SDS, named Shwachman-Bodian-Diamond syndrome (SBDS) gene.  D. Johanna Rommens and her colleagues from the Hospital for Sick Children in Toronto are to be credited with this important work. 

The gene is:

• at chromosome 7, near the centromere
• a small gene, with 5 exons (coding re gions)
• accompanied by a pseudogene, with 97% identity
• identified in many tissues, and highly conserved (seen in many life forms)

The encoded protein, and function, from that gene are not yet identified.  The authors have identified 3 main mutations and 27 minor mutations:  75% are on exon 2.

Molecular Diagnostic Testing - Genetic Counselling

Since clinical diagnosis may be difficult, genetic testing could help confirm SDS.  Dr. Peter Ray is developing diagnostic tests to better detect the mutations causing SDS.

Problems:

• multiple rare mutations
• pseudogene similar to SBDS

Plan:

• initial testing for 3 common mutations or exon - 2 using SNPs (single nucleotide polymorphisms-amplifying only the SBDS gene, not the pseudogene)
• then, if necessary, sequencing the 5 exons to detect rare mutations

Genetic counseling is even more important at this stage.  Ms. Nada Quercia is a genetic counselor, and she explained that she and her colleagues can provide information to help understand the nature of the genetic condition, how it is inherited, what are the possible recurrent risks of another similarly affected child, and how to interpret the results of genetic tests, and what are available options for family planning.

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