Successful PGD for late infantile neuronal ceroid lipofuscinosis achieved by combined chromosome and TPP1 gene analysis

Late infantile neuronal ceroid lipofuscinosis (NCL-2) is a severe debilitating autosomal recessive disease caused by mutations in TPP1. There are no effective treatments, resulting in early childhood death. A couple with two affected children presented for reproductive genetic counselling and chose to undertake IVF and preimplantation genetic diagnosis (PGD) to avoid the possibility of another affected child. However, DNA testing revealed only one mutation in the proband inherited from mother. Linkage analysis identified five informative linked short tandem repeat markers to aid the genetic diagnosis. Following IVF, five cleavage-stage embryos were biopsied and blastomeres were first subjected to whole-genome amplification, then a series of down-stream molecular genetic analyses to diagnose TPP1 genotype and finally array comparative genomic hybridization (CGH) to assess the chromosomal ploidy of each embryo. Two unaffected euploid embryos were identified for transfer. One was transferred on day 5 resulting in an ongoing pregnancy. Confirmatory prenatal diagnosis by amniocentesis showed concordance of the embryo and fetal diagnosis. As far as is known, this is the first successful report of PGD for NCL-2 using double-factor PGD with simultaneous single-gene testing and array CGH to identify an unaffected and chromosomally normal embryo for transfer.Late infantile neuronal ceroid lipofuscinosis (NCL-2) is a severe debilitating disease associated with epilepsy, muscle weakness and mental deterioration that leads to early childhood death. A couple who naturally conceived two children affected with NCL-2 presented for genetic counselling to consider their reproductive options. One of their children had since died from the disease. They chose IVF and preimplantation genetic diagnosis so that they could start their pregnancy knowing that their baby was unaffected with the disease. Both partners and the one surviving child underwent DNA testing and one of the two causative mutations was identified in the TPP1 gene. A molecular diagnostic test was subsequently developed using whole-genome amplification combined with TPP1 gene analysis of the mutation and additional five gene markers. After ovarian stimulation, five mature eggs collected from the mother were fertilized by the father’s spermatozoa and the resulting embryos successfully cultured for 3 days to the cleavage-stage of development. A single cell was biopsied from each embryo, the DNA replicated by whole-genome amplification and then the amplified DNA products subjected to detailed molecular testing to analyse the status of the TPP1 gene as well as the chromosome karyotype. Two disease-free and chromosomally normal embryos were identified and the highest quality embryo was subsequently transferred to the mother’s uterus and a singleton pregnancy resulted. The original embryo diagnosis was subsequently confirmed by amniocentesis as unaffected and the healthy pregnancy is anticipated to proceed to term. As far as is known, this is the first successful report of PGD for NCL-2.