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  Carlo Gambacorti: DIAG: 2 messages: "the future of genetic newborn screening", Asian DNAs  
   

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To: Multiple recipients of list HUM-MOLGEN <HUM-MOLGEN@NIC.SURFNET.NL>
Subject: DIAG: 2 messages: "the future of genetic newborn screening", Asian DNAs
From: Carlo Gambacorti <GAMBACORTI@icil64.cilea.it>
Date: Thu, 10 Aug 1995 09:35:30 MET-DST

**************************************************************
           HUM-MOLGEN  DIAGnostics/Clinical Research
**************************************************************


This DIAG message contains  submessage(s):

1)   The future of newborn screening, From: "Brian Mannix (mmatrix)"
     <BMannix@AOL.COM> + a comment from the editor


2)   Asian DNAs



  Carlo Gambacorti MD, Editor,
  Human Molecular Genetics network
  Diagnostics/Clinical Research Section


**************************************************************
**************************************************************

I would like to stimulate some discussion on the ways that genetic technology
may be used to improve newborn metabolic screening programs.  (for PKU,
galactosemia, maple syrup urine disease, etc.).  I offer the following rough
protocol for comment.

1) At birth, the physician recovers as much cord blood as possible and sends
it to a lab.

2) The lab uses genetic probes to test for the usual metabolic disorders, as
well as other common genetic errors (e.g., CF).

3) Samples that test normal are discarded; samples that test positive are
transformed to contain the appropriate normal alleles.

4) The transformed cells are transfused back into the infant to provide some
nominal level of enzyme activity.  Since cord blood contains stem cells, this
enzyme activity could, in principle, last a lifetime.

Compared to today's technology, such a protocol would provide faster and more
accurate diagnoses, could be expanded to many more birth defects, and could
provide a possible therapeutic benefit.

On the other hand, there are some obvious disadvantages as well.  The
protocol above would always be more expensive than today's screening tests,
if only because of the volume of blood involved.  Moreover, while using cord
blood may save the infant a heel stick, it is hardly convenient:  there is a
lot going on during a typical birth that is more urgent than collecting a
screening sample.  And, of course, it may turn out that very few genetic
diseases would benefit from a simple transfusion of transformed stem cells.

Because of these shortcomings, such as system might be used, at best, only on
a subset of diseases for a subset of at-risk births.  Nonetheless, I think it
is useful to speculate along these lines, and I welcome any and all comments.

Brian Mannix
Bmannix@aol.com

EDITOR'S NOTE
     This is enticing and intriguing message and should be read for what it
is.
Several items must be considered when reading it:
- genetic tests are not yet available for many inherited diseases, and
therefore
the possibilities to correct the defect are not therefore available;
- since the results of the tests are not immediate, it would need to store
many samples, with a very significant cost (a sensitive item today, who
should pay for ?);
- the correction is not guaranteed by the transformed cells. Some diseases
(like CF) are unlikely to be affected by the infusion of cord blood cells, in
addition there is no
proof at present that these cells will persist for a long term; they can be
immunologically rejected (because of the new viral and cellular genes intro
duced). The transplant, even if autologous, would require a certain
degree of immunosuppression of the host, and therefore would carry its own
burden of toxicity and risk.
Mass collection of cord blood seems also problematic; an alternative
could be to carry it out in selected cases (carrier families, prenatal
diagnosis...).

Carlo Gambacorti MD

**************************************************************


        We have recently identified a highly polymorphic Y chromosome marker
and are currently genotyping it on Caucasian, African-American and American
Indian DNAs. We would also like to genotype it on a comparable collection of
Asian DNAs. If anyone has such a collection and is interested in collaborating
please get in touch with me.
Don Bowden
Bowman Gray School of Medicine
Winston-Salem, NC
Donald Bowden <BOWDEN@MGRP.BGSM.WFU.EDU>


   
 
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