PATERNAL MITOCHONDRIAL-DNA TRANSFERRED TO THE OFFSPRING FOLLOWING INTRACYTOPLASMIC SPERM INJECTION

During intracytoplasmic sperm injection (ICSI) the whole sperm, includ ing head, midpiece and tail, is injected into the middle area of the o ocyte. To find out what happens to the sperm mitochondria after ICSI, we checked the first six children born after ICSI treatment for occurr ence of paternal mitochondrial DNA (mtDNA). The difference between mat ernal and paternal mtDNA in the investigated couples in our study war; confined to single-base pair substitutions and we had to rely on rest riction enzyme cleavage to differentiate between the mitochondrial gen omes of the parents. With this kind of assay we were able to reach a s ensitivity of about 0.2% for the paternal mtDNA. However as uneven par tition between tissues of heteroplasmic mtDNA is expected to occur; it would not be unlikely that an enrichment to 0.2% would occur in a giv en tissue if paternal mtDNA was transmitted by the ICSI procedure, We did not detect this level in the blood in any of the six children.