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Genomic cosmid contig spanning the tl'anslocation breakpoint
Two chromosome 22 specific cosmid libraries (LL22NCOI and LL22NC03) were used to
isolate a contig starting from D22SI93. This resulted in the isolation of four overlapping
cosmids, which were used to construct a genomic EcoRI restriction map encompassing 120
kb (Fig.2). Further details concerning the isolation and construction of the map are given in
the methodology section. To investigate the localization of the newly isolated cosmids relative
to the breakpoint we used these cosmids and isolated restriction fragments for fluorescent in
situ hybridization (FISH) on metaphase chromosomes and southern hybridization on DNA
derived from the hybrid cell lines segregating the translocation products. Both approaches
confirmed that the position of the breakpoint was confined in the contig (results not shown).
Further mapping revealed that the breakpoint was located on a 8 kb genomic EcoRI fragment
(Fig.2, see below).
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1(4;22)
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UNI eDNA "-, ,
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3' probe 022$193 ~
genomic fragments =
Cosmid contlg
--------- 58B12
76M --------4002
---------- 50BlI
o
10 20 30 40 60 70 80 90 100 110 kb
Telomere
Centromere
Figure 2.
Physical map around the t(4;22) breakpoint and the MNI gene on chromosome 22qll. The
deduced EcoRI (E) restiction map with the localization of the t(4;22) breakpoint, the complete
MNl eDNA and cDNA clone 17,1 (probe 17.1) are shown. One EcoRI site is lifted from the map
because its exact localization within the map is unknown. The overlapping cosmids spanning this
region are shown at the bottom from telomere to centromere. The genomic fragments used to
screen the eDNA library are indicated by open hoxes.
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