Question
To ask Her Majesty’s Government, further to the Written Answer by Lord Marland on 19 November (WA 311–12), in what ways lessons from pronuclear transfer (PNT) can inform somatic cell nuclear transfer (SCNT) research; whether PNT involves direct transfer of the DNA in the sperm and the egg; why they have stated that the genetic identity of a PNT embryo is unique only to the sperm and egg from which the pronuclei are formed, rather than to an embryo as defined in the Human Fertilisation and Embryology Act 2008; and on what basis the Human Fertilisation and Embryology Authority has described PNT as “mitochondria replacement” in its consultation Medical frontiers: debating mitochondria replacement.[HL3684]
Answer
The department has sought advice from medical researchers through the Medical Research Council. Their advice is that researchers have found that the technical challenges associated with pronuclear transfer (PNT) are very similar to those of somatic cell nuclear transfer (SCNT). Therefore it is understood that the optimisation of one technique informs the development of the other.
The PNT procedure involves transferring the DNA from the egg and the DNA from the sperm, which are separately packaged in two distinct structures known as the pronuclei.
The genetic identities of the maternal and paternal pronuclei are unique to the egg and sperm from which they are derived. Nuclei containing the two sets
of DNA, which confer the unique identity of the embryo, are not normally formed until after the fertilised egg divides to form a two-cell embryo. The Human Fertilisation and Embryology Act defines both developmental stages as embryos.
The Human Fertilisation and Embryology Authority (HFEA) has informed me that the term “mitochondria replacement” has been used to describe PNT and maternal spindle transfer (MST) in its consultation “Medical Frontiers: debating mitochondria replacement”. The aim in using such terminology was to enable a lay audience to understand the essential purpose of these techniques.