IVF Strategies: Cloned Sperm and Preimplantation Genetic Diagnosis

IVF Strategies: Cloned Sperm and Preimplantation Genetic Diagnosis

by Dr. Hsien-Hsien Lei
Posted July 5, 2007 in DNA Testing, DNA and Disease, DNA in General, Genetic Engineering

spern lightsTraditional wisdom tells us that men can father children at any age while women’s biological clocks implode in their late 40’s or 50’s. But, according to IVF.com, male infertility occurs in 50% of cases where a couple can’t conceive. A number of causes can lead to male infertility including abnormal sperm; about one in 300 men have extremely low sperm counts. In these cases, scientists hope that cloning human sperm will be an option in the future.

Cloned sperm used to fertilise mouse eggs have resulted in the birth of healthy mice (along with quite a few that died shortly after birth). The cloned sperm were created by:

  1. Injecting normal sperm heads containing DNA into eggs that had that its own DNA removed, letting the eggs divide creating “pseudosperm.”
  2. Fertilizing normal mouse eggs with the pseudosperm creating embryos
  3. Transferring the embryos to female mice

Among the unknowns, sperm DNA apparently stops expressing male-specific genes after three rounds of cell division as a pseudosperm. Does that mean resulting embryos would all be female? Or does it also mean genes responsible for testosterone and other male hormones would be affected as well?

In related news, Dutch researchers have shown that preimplantation genetic diagnosis (PGD) may not help older women become mothers. PGD is used to screen embryos for genetic defects by sampling one cell from a 3-day-old embryo. By only implanting embryos that do not have any observable genetic defects, doctors hoped to increase the pregnancy success rate in older mothers undergoing IVF. However, results from a study of 408 women who were assigned to receive either IVF with or without PGD found that women undergoing PGD actually had a lower rate of successful births – 24% compared to 35% in women who underwent IVF alone. (More on PGD at the UK Human Fertilisation & Embryology Authority website.)

Infertility seems to be in the news this week. For personal stories on infertility, start at a little pregnant where Julie has created a list of infertility blogs.

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3 Comments

[...] IVF Strategies: Cloned Sperm and Preimplantation Genetic Diagnosis by Hsien-Hsien at Eye on DNA [...]

 

[...] experts are up in arms over recent data showing a lack of benefit from preimplantation genetic diagnosis (PGD) in improving pregnancy success in older women. They cite “the authors’ poor embryo [...]

 

[...] Sperm produced by mice exposed to air pollution have been found to have more genetic mutations and DNA methylation. Not to worry – just use cloned sperm! [...]

 

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