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BlueGnome Licenses Karyomapping IP in Bid to Bolster Pre-Implantation Genetic-Dx Play

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By Justin Petrone

BlueGnome this week acquired intellectual property for karyomapping technology in an effort to carve out a bigger chunk of the pre-implantation genetic-diagnostic market.

CEO Nick Haan said that karyomapping, which uses SNP genotyping to screen for genetic disorders in embryos, will complement BlueGnome's 24sure offering, which relies on a bacterial artificial chromosome array and software to confirm that eggs and embryos contain the correct number of chromosomes prior to implantation in an in vitro fertilization cycle.

Cambridge, UK-based BlueGnome launched 24sure last year, and last month established a new company, called Sure Laboratories, also based in Cambridge, to support the service (BAN 9/7/2010).

"We aim to address diagnosis of single-gene disorders using SNP-array technology," Haan told BioArray News this week. "Karyomapping is the first technique which enables single-gene testing sufficiently robustly for routine clinical use," he said. "It also has advantages of determining inheritance patterns across the genome."

BlueGnome acquired the karyomapping IP from inventor Alan Handyside and the London Bridge Fertility, Gynaecology, and Genetics Centre, where Handyside is the scientific director. As part of the deal, Handyside has joined BlueGnome as head scientist of pre-implantation genetics.

According to Haan, karyomapping relies on the ability to obtain SNP-genotype information from relatives, such as parents and grandparents, as well as those who are known to carry a deleterious gene. By matching the SNP genotypes of embryos to relatives, and knowing where the deleterious gene resides, it is possible to infer the status of the embryo, Haan said.

The firm's ultimate goal is to use arrays and other technology to "significantly improve IVF success rates," he said. The company's 24Sure technology will in the future not only have the ability to screen eggs and embryos for aneuploidy, but also single-gene conditions.

"Karyomapping allows us to be able to offer a new product which can screen for single-gene disorders in single cells," said Haan. He did not elaborate on when the new product will become available. Haan said that Sure Labs will use karyomapping in the future and that Handyside will eventually play a role in the new cytogenetic laboratory services firm, though "not at this stage."

Handyside said in a statement that he joined BlueGnome because its "24sure platform has already established itself as the standard for screening the very large-scale chromosomal imbalances that are thought to be a major cause of infertility."

The company now has an "opportunity to extend this approach to the inheritance of some truly debilitating genetic disorders," he said in the statement.

PGD

Pre-implantation genetic diagnosis, or PGD, is used in combination with IVF approaches where there is a risk of severe genetic disorders being inherited from parents. PGD screening is used to identify embryos that do not carry defective genes and to identify those that can be safely implanted.

Current methods rely on PCR, though BlueGnome describes this approach as "expensive, time-consuming, and only available at a small number of very specialist laboratories." Karyomapping, in contrast, is a genome-wide method that eliminates the need to develop specific PCR assays for each gene defect.

Handyside and colleagues described their approach in a recent Journal of Medical Genetics paper in which they used Illumina HumanCNV370 Infinium-II Quad and Duo BeadChips to establish genotypes of parents, siblings, or other appropriate family members. This information was used to identify informative loci for each of the four parental haplotypes across each chromosome and map the inheritance of these haplotypes and the position of any crossovers.

According to the authors, the resulting "karyomap" identifies the parental and grandparental origin of each chromosome and chromosome segment and is "unique for every individual being defined by the independent segregation of parental chromosomes and the pattern of non-recombinant and recombinant chromosomes."

Karyomapping, the authors write, "enables both genome-wide, linkage-based analysis of inheritance and detection of chromosome imbalance where either both haplotypes from one parent are present or neither are present."

The paper's authors outline several "major" applications of their technology. One is for carriers of "balanced structural chromosome abnormalities, mainly reciprocal and Robertsonian translocations, which can cause infertility or repeated miscarriage."

Another "important" application is for human leucocyte antigen matching, "with or without single gene-defect testing if required, with the aim of isolating cord blood stem cells at birth for transplantation to an existing child with a serious blood related illness."

The authors do note a few drawbacks to the technique, such as the "relatively expensive" use of arrays when compared with standard methods, though they believe that arrays will ultimately help labs cut down on labor costs. They also cite "challenging clinical and ethical issues" inherent in using a genome-wide approach for pre-implantation genetic diagnosis, as counselors might be compelled to inform clients of de novo mutations that may be hard to interpret.

The authors suggest blinding the study to only look at information contained in the karyomap. "If deemed necessary, it would be straightforward to blind or remove some or all of the genotype data from clinical records," they suggest.

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