To ask Her Majesty’s Government, further to the Written Answer by Earl Howe on 15 December (HL3302), how exhaustively the POLG gene at chromosomal locus 15q25 has been sequenced in all individuals known to be affected by the mitochondrial diseases listed in Annex D of the mitochondrial donation consultation document in order to establish the evidence base described in that answer; and whether the Human Fertilisation and Embryology Authority would routinely require sequencing of the POLG gene in order to ensure that pronuclear transfer or spindle-chromosomal transfer should only be used for patients who have an inherited mitochondrial DNA mutation and not where faulty mitochondria may have arisen from a nuclear gene mutation.
Answered on
5 January 2015
We are advised by the Wellcome Trust that diagnosis of mitochondrial DNA disease is performed within the National Health Service Highly Specialised Service diagnostic laboratory using well established diagnostic algorithms and Practice Guidelines for the Molecular Diagnosis of Mitochondrial Diseases published by the Clinical Molecular Genetics Society at:
http://www.acgs.uk.com/media/774654/mito_2008.pdf
Mitochondrial defects that arise due to nuclear gene mutations, such as DNA polymerase gamma, routinely give rise to multiple different mutations of mitochondrial DNA within patient tissues or depletion of mitochondrial DNA. This is apparent upon genetic testing and would then lead to analysis of the DNA polymerase gamma gene to identify the nuclear gene defect.
The Human Fertilisation and Embryology Authority has advised that it will design the regulatory process following the passage of any regulations to allow mitochondrial donation. Should Parliament pass the mitochondrial donation regulations, the technique could only be licensed for the avoidance of diseases caused by inherited mutations in mitochondrial DNA, not nuclear DNA.