From eleanor@XXXX Fri Aug 23  12:23:37  1996
From: Eleanor Whitfield (Genetics) <eleanor@XXXX>
Date: Fri, 23 Aug 96  12:23:35  BST
To: baker@XXXX
Subject: Help FlyBase - wgCX3
Cc: eleanor@XXXX
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Hi Nicholas,
I am a curator for FlyBase working at the Cambridge, England, site with
Prof M. Ashburner. While curating a paper I came across wgCX3, of course
now known as wgl-16. I went to all the references we have listed for
wgCX3 and it soon became apparent that this chromosome is a little
confusing. I was hoping you could help me to clear this up.
\*x FBrf0046100 == Baker, 1987, EMBO J. 6(6): 1765--1774
reports a breakpoint between +10.8 and +15.0 of the wg molecular map, this
is a complex rearrangement and not a deficiency.
\*x FBrf0047884 == Baker, 1988, Development 102: 489--497
reports a breakpoint downstream of the transcription unit that brings other
sequences close to the 3' terminus of wg. Deletion of other genes other
than wg.
\*x FBrf0066940 == van den Heuvel et al., 1993, EMBO J. 12: 5293--5302
reports a 17kb insertion of unknown DNA between 2-4kb from the
transcriptional endpoint of wg.
Could you please clarify the situation?
Many thanks
Eleanor Whitfield
FlyBase
From baker@XXXX Fri Aug 23  15:32:57  1996
Date: Fri, 23 Aug 1996  10:23:58  -0400 (EDT)
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To: Eleanor Whitfield (Genetics) <eleanor@XXXX>
From: baker@XXXX (Dr. Nicholas Baker)
Subject: Re: Help FlyBase - wgCX3
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Dear Eleanor,
Sorry that wgCX3 is so confusing. The allele was X-ray induced,
and based on orcein squashes appeared to involve a deficiency ~28A-C.
Homozygous embryos died before secreting cuticle, consistent with deletion
of many genes. In trans to null alleles of wg, wgCX3 gave pupal lethality,
indicating that it is not a null allele of wg, which cannot have been
deleted in wgCX3. Southern blotting showed that most of the wg gene was
unaltered but there was a breakpoint in the +14.6 - +16.3 interval. To
test whether this was one end of a deficiency, blots were performed with
wgCX3/wg1 DNA, since wg1 deletes some DNA right of +16.3, but this DNA was
still present in the wgCX3 chromosome. From this I concluded that the 3'
breakpoint in wgCX3 was not one end of a deficiency. The relationship of
the wgCX3 lesion to the cytology of the chromosome was not clear; they
might be related parts of a complex rearrangement, or might be independent
events in the same chromosomal region.
I understand the van den Heuvel et al to have shown a 17kb
insertion into wgCX3. I assume this is the event in the +14.6-+16.3
interval that I identified in Southern blots. As I recall, their paper
gives no further insight as to the cytological appearance of wgCX3, or to
the apparent mutation of other genes required to account for the arrest of
wgCX3 homozygotes prior to embryonic cuticle secretion. Marcel van den
Heuvel (now with Phil Ingham??) might have further unpublished data, but
unless he does so you can draw no inference of any deletion associated with
the insertion, or anywhere else in the cloned wg region, and the reason for
the altered cytology is unclear and very possibly unrelated to wg.
hope this helps,
regards
Nick Baker
From eleanor@XXXX Fri Aug 23  16:06:10  1996
From: Eleanor Whitfield (Genetics) <eleanor@XXXX>
Date: Fri, 23 Aug 96  16:05:50  BST
To: baker@XXXX
Subject: Re: Help FlyBase - wgCX3
Cc: eleanor@XXXX
Content-Length: 952
Hi Nick,
Thank you very much for your prompt reply, it is always appreciated.
I am now clear about the complete picture of the chromosome rearrangements
given in your papers, thank you. If you have no objections I would like to
curate your correspondance as a personal communication to FlyBase.
Many thanks for your help,
Eleanor Whitfield
From baker@XXXX Fri Aug 23  16:55:40  1996
Date: Fri, 23 Aug 1996  11:46:39  -0400 (EDT)
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To: Eleanor Whitfield (Genetics) <eleanor@XXXX>
From: baker@XXXX (Dr. Nicholas Baker)
Subject: Re: Help FlyBase - wgCX3
Content-Length: 2024
Dear Eleanor,
Having checked in my thesis I see that I said wgCX3 was a
deficiency in 28A. There is a photo there and it looks like it might go
into 28B but I don't want to be quoted on this based on memory from a
decade ago. Please can you leave it as 'small deficiency in 28A region' -
unless anyone wants to do a careful cytological analysis.
By all means include my message in fly base. Everything in it is
in my thesis 'wingless: a gene required for segmentation in Drosophila',
Univ. of Cambridge 1986, and this may be more appropriate than pers. comm.
However, the details could also be summarised as: 'the wgCX3
mutation is associated with an insertion of unknown DNA just 3' to the
transcription unit (Baker 1987; van den Heuvel 1993). In addition, the
cytological appearance of a deletion in 28A and the early demise of wgCX3
homozygous embryos prior to cuticle secretion imply deletion or alteration
of other genes, but the molecular basis has not been determined (Baker
1988).'
regards
Nick Baker