Improved single-cell protocol for preimplantation genetic diagnosis of spinal muscular atrophy

Objective: To develop and validate a simple and reliable single-cell analysis protocol for the preimplantation genetic diagnosis (PGD) of spinal muscular atrophy (SMA). Design: Molecular tests based on specific enzymatic digestion have already been described for SMA diagnosis. We modified the amplified DNA fragments so as to introduce a novel restriction site that provides an internal control for the completeness of the digestion. Setting: The genetics and reproduction departments of two teaching hospitals. Patient(s): Six informed couples at risk of transmitting SMA. Intervention(s): All patients underwent standard procedures associated with intracytoplasmic sperm injection. Main Outcome Measure(s): improvement of SMA diagnostic efficiency and accuracy on single cell. Result(s): One hundred fifty lymphocytes were analyzed with our protocol. One hundred percent diagnostic accuracy was achieved from both homozygous normal and SMN1-deleted leukocytes. Successful molecular analysis was achieved for 36 of 42 biopsied embryos (86%). Twenty-five normal embryos were transferred, but no pregnancy was achieved. Conclusion(s): We developed an improved protocol for PGD of SMA that is simple, robust, and accurate; unfortunately, no pregnancies were achieved for any of the six patients who have undergone PGD in the program thus far.