But it still needs a bit of work. [email protected] Reprogenetics ART Institute of Washington Life...
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MRT – A Great Idea but it still needs a bit of
But it still needs a bit of work. [email protected] Reprogenetics ART Institute of Washington Life Global Principle investigator of cytoplasmic transfer
[email protected] Reprogenetics ART Institute of Washington Life
Global Principle investigator of cytoplasmic transfer series
(1996-2001)
Slide 3
Is there an alternative to MRT? Lessons from the cytoplasmic
transfer series Cellular stress from micromanipulation? (safety)
Preferred technical approach (MST, PNT, PBT)? Nomenclature?
Slide 4
Slide 5
YES Preimplantation Genetic Diagnosis or PGD (PGD for
mitochondrial disease) Use of PGD varies from 3-85% (USA data)
Usage in Europe mostly limited to early embryo stages (.)
Blastocyst culture increases success rates Allows biopsy of a
better sample Cryopreservation survival higher with blastocysts
Evidence shows PGS is successful at blastocyst
Slide 6
Less than 50 cases of PGD for Mito Disease About a dozen papers
(using pb or blastomere biopsy) Shows reliability increases with
cell and egg number Shows little variation in mutation load PGD for
mito disease should be considered at blastocyst stage in
combination with vitrification
Slide 7
Sallevelt et al, 2013
Slide 8
Slide 9
Mid-90s state of assisted reproduction Acceptable pregnancy
rates achieved by multiple embryo transfer Early knowledge about
embryonic aneuploidy and age Cytoplasmic failure seemed a
reasonable proposition Selected patients with multiple failed IVF,
poor embryo development but. NOT increased maternal age Three
patient cycles using electro-fusion of cytoplasts Increased
abnormal fertilization (same as MRT work) Changed technology to
cytoplasmic transfer by injection Based on ICSI for male factor
(>50,000 babies) Cohen et al, 1997 and 1998
Slide 10
Cohen et al, 1998
Slide 11
37 cycles (33 patients) 17 babies born 12 deliveries 1 early XO
miscarriage 1 late XO termination One male twin at 18 months
borderline PDD-NOS Two babies confirmed with donor mitochondria in
a series of n=8 Heteroplasmy First phase follow-up study 2014-2015
Preliminary data is reassuring Cohen et al, 1997, 1998, 1999;
Brenner et al 2000, Barritt et al, 2001
Slide 12
Two types of experiments Using combinations of two inbred
species: heteroplasmic mice are developmentally affected (minor to
major) Using inter-strain and F1 hybrids: (no effect or minor)
Inbred - At least 20 consecutive generations of sibling or
parent/offspring mating Inbred mice are homozygous at virtually all
of their loci We are not an inbred species Acton et al, 2007 Liang
et al, 2009 - Cheng et al, 2009 We find that inter-strain mPNT, ST,
and ooplasm transfer produce little or no long-term adverse effects
on growth rate or methylation states of the genes assayed.
Slide 13
Slide 14
Seen after all forms of manipulation But can be minor (ICSI)
Cytoplasmic transfer (CT) similar to ICSI CT pilot study using ICSI
(>50,000 ICSI babies in 1996) Electrofusion - no prior
alternative (0 babies) Sendai Virus Extract (SeV) (0 babies)
Membrane relaxants (0 babies)
Slide 15
Two implantations with XO after CT Possibly significant
Possibly related to cellular stress (XO can occur during formation
of pb2) Strongly recommend PGS after MRT to confirm normal
chromosome set
Slide 16
Slide 17
Polar body transfer (PBT) was successfully used to model MRT in
the mouse (Wang et al, 2014) Highly successful in the mouse In some
mouse strains polar bodies are sometimes viable (.) In the human
they are very different from patient to patient
Slide 18
Slide 19
Changing genes which are passed on to future generations or
changing genes in gametes and very early embryos [meaning not
temporarily as in altered gene expression but changing the code].
Maybe but the altered genes already existed in someone else. It is
the combination of nDNA and mtDNA that is novel, but that
descriptive is similar to each new fertilization.
Slide 20
Gene therapy is an experimental technique that uses genes to
treat or prevent disease. In the future, this technique may allow
treatment of a disorder by inserting a gene into a patient's cells
instead of using drugs or surgery. Yes, very close, maybe a
specialized form? - Gene therapy is an experimental technique that
uses someone elses genes to treat or prevent disease. Applies to
MRT. Does it apply to CT?.
Slide 21
or Genetic Engineering. Genetic engineering is the process of
manually adding new DNA to an organism. The goal is to add one or
more new traits that are not already found in that organism. This
probably does not apply. No likely addition of new traits. Addition
of new traits is not the goal.