Isolation of Two Novel Genes, DSCR5 and DSCR6, from Down Syndrome Critical Region on Human Chromosom

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Isolation of Two Novel Genes, DSCR5 and DSCR6,
from Down Syndrome Critical Region on Human
Chromosome 21q22.2 Presenter Ryan Purcell,
Creator Allison Kelliher, Reviewer Andy Krohn,
Manager Adrienne Tveit
Introduction Down syndrome (DS) is the most
common birth defect. 1/1000 children are born
with DS.Characteristics of this disorder include,
mental retardation, congenital heart disease,
facial and physical features, defects of immune
and endocrine system. DS is caused by complete
or partial trisomy of chromosome 21.(Fig 1) Two
genes have been isolated from the Down Syndrome
critical Region (DSCR). This region lies on
Chromosome 21q22.12.(Fig 2) These novel genes
are designated DSCR5 and DSCR6. DSCR5 codes for
three transmembrane proteins. DSCR6 codes for two
proteins. DSCR5 is expressed in various tissues,
whereas DSCR6 is less expressed in fewer tissues.
Six genes have been found in the DSCR, but many
more must be analyzed in order to determine their
roles in the pathogenesis of Down Syndrome. The
BAC (bacterial artificial chromosome) clone
KB318C was analyzed by shotgum sequencing
method.(Fig 3)
Figure 4. RACE is a procedure which amplifies
the ends of the DNA through a mechanism similar
to PCR.

• Methods
• Shot-Gun sequencing of BAC clone, KB318C2 was
  utilized in order to determine BAC clone.
• Results were analyzed via Gen-Bank
• RACE (Rapid Amplification of cDNA(clone) ends)
  and PCR were performed
• Expand High Fidelity PCR System used on DSCR5 and
  6 and cDNA
• 94 C for 30 sec, 65 C for 1 min, and 72 C for 2
  min for 35 cycles in automated thermal cycler
• DNA sequencer utilized DideoxyTerminator Cycle
  Sequencing method.
• Expression analyzed by Human Multiple Tissue cDNA
  (MTC) panels which had 27 human tissues. PCR
  performed as a control of all MTC tissues.

• Results
• Expression pattern ofDSCR5a, DSCR5b, DSCR5c,
  DSCR6a, and DSCR6b were analyzed using MTC
• DSCR5a and DSCR5b were expressed in many tissues
• DSCR5c expressed in fetal liver but not in any
  adult tissues except for the testis
• DSCR6a and DSCR6b are expressed in fetal kidney
• DSCR6b is higher in fetal brain
• DSCR6a and DSCR6b were expressed at very low
  levels in adult kidney and brain

• Conclusions
• 122,672 nucleotide sequence of BAC clone, KB318C2
  was determined
• DSCR5c was not found in adult tissues except for
  in testis. Further analysis must be performed to
  determine if it is functionally active in early
  embryogenesis.
• DSCR5 and 6 have unknown function, but because
  they are found in the DSCR and have possible
  function in early embryogenesis they are
  candidates for pathogenesis of DS

Figure 3. The strategy for determining BAC
sequence. Shotgun libraries are constructed in
plasmid vectors and M13 using hydrodynamically
sheared BAC or YAC (Yeast artificial chromosome)
DNA. Subclones will be sequenced randomly. The
subclone sequences will be assembled into contigs
using software. The gaps between contigs will be
closed by "primer walking" on plasmids or BACs.
Acknowledgements Shibuya K., Kudoh J., Minoshima
S., Kawasaki K., Asakawa S., and Shimizu N.
Isolation of Two Novel Genes, DSCR5 and DSCR6,
from Down Syndrome Critical Region on Human
Chromosome 21q22.2 9. Biochemical and
Biophysical Research Communications 271, 693-698
(2000) Novel Genes, http//pgec-genome.pw.usda.gov
/bac-strategy.html