Mapping of the mouse hyh gene to a YAC/BAC contig on proximal
Teresa H. Chae,
* Kristina M. Allen,
** Muriel T. Davisson,
Hope O. Sweet,
Christopher A. Walsh
Dept. of Neurology, Beth Israel Deaconess Medical Center, Harvard Institutes of Medicine, Room 816, 77 Avenue Louis Pasteur,
Boston, Massachusetts 02115, USA
The Jackson Laboratory, Bar Harbor, Maine 04609-1500, USA
Received: 22 October 2001 / Accepted: 10 January 2002
Abstract. Mice that are homozygous for the autosomal recessive
hydrocephaly with hop gait (hyh) mutation on Chromosome (Chr)
7 have congenital hydrocephalus characterized by an interhemi-
spheric cyst arising from the third ventricle and agenesis of the
corpus callosum. Analysis of more than 500 backcross and inter-
cross progeny maps the hyh locus to proximal Chr 7, approxi-
mately 13 cM centromeric to its originally reported map position.
Analysis of recombinants at several MIT microsatellite markers
localized the hyh locus between D7Mit75 and D7Mit56. Develop-
ment of several new SSLP markers allowed us to refine the hyh
candidate interval to a region defined by the cone-rod homeobox
(Crx) gene proximally and D7Mit56 distally. A contig of yeast
artificial chromosome (YAC) clones and bacterial artificial chro-
mosome (BAC) clones spanning this entire region has been devel-
oped, and a number of potential candidate genes for hyh within this
interval have been identified. Gene content is conserved between
this region of mouse Chr 7 and human Chr 19q13.3. Physical
mapping of the regions around D7Mit75 and D7Mit56 has also
determined the order of a number of MIT markers that remain
unresolved on the Mouse Genome Database (MGD) map. Our
physical map and transcript map may be useful for positional
cloning of genes in this unusually gene-rich region of the genome.
The mouse mutant hydrocephalus with hop gait (hyh) is one in a
series of spontaneous mouse mutants with autosomal recessive
forms of hydrocephalus (Bronson and Lane 1990). Several of these
hydrocephalic mice show otherwise normal brain development.
However, in other hydrocephalic mice, including congenital hy-
) (Green 1970; Kume et al. 1998), hydroce-
) (Hollander 1976), hydrocephalus 1
(hy1) (Clark 1932), and hyh, the hydrocephalus reflects a wide-
spread developmental anomaly of the brain. These mouse mutants
may represent important animal models for human congenital hy-
drocephalus, which is etiologically heterogeneous, but also define
genes required for normal brain patterning.
The most striking aspect of the hyh phenotype is the dramatic
cystic dilation of the third ventricle and dilatation of the lateral
ventricles and caudal aqueduct that are present at birth and pro-
gressively worsen with age (Bronson and Lane 1990). In humans,
hydrocephalus is rarely caused by overproduction of cerebrospinal
fluid (CSF), but rather by blockage of CSF flow. Interestingly, in
the hyh mouse there appears to be no blockage of CSF flow within
the ventricular system at birth, although there is extensive expan-
sion of the ventricles (Perez-Figares et al. 1998). Therefore, the
exact etiology of the hydrocephalus is still uncertain.
Extensive ependymal denudation has been observed during
embryogenesis prior to expansion of the ventricles (Jimenez et al.
2001). The third ventricular cyst eventually displaces other midline
structures and extends between the cerebral hemispheres. Wors-
ening hydrocephalus leads to doming of the head and probably is
responsible for lethality within weeks to a few months after birth.
Other abnormalities of note are the failure of corpus callosum
fibers to cross the midline, instead forming Probst bundles on
either side of the expanded third ventricle, disorganization of neu-
rons in the rostral vermis of the cerebellum (Bronson and Lane
1990), and complete absence of the central canal of the spinal cord
(Perez-Figares et al. 1998).
We have undertaken the genetic and physical mapping of the
hyh gene. The hyh gene was originally mapped to about 15.2 cM
from the centromere of Chr 7 on the basis of intercrosses with 80
meioses, by using visible and eletrophoretic markers (Bronson and
Lane 1990). We have localized hyh more precisely to proximal Chr
7, approximately 13 cM away from its originally reported location.
A complete YAC/BAC contig of this region has been generated,
and a number of candidate genes for hyh have been identified,
establishing conservation between the hyh candidate interval and
human Chr 19q13.3, one of the most gene-rich regions of the
human genome (Lander et al. 2001; Venter et al. 2001). Our physi-
cal mapping has also ordered a number of MIT markers that re-
main unresolved on the Mouse Genome Database map (MGD
2001) and has generated several new polymorphic microsatellite
markers. These data should be useful to other researchers under-
taking positional cloning of genes on proximal Chr 7.
Materials and methods
Animals and matings.
Mice were obtained from The Jackson Labora-
tory (Bar Harbor, Me.) where the hyh mutation originally arose in the
C57BL/10J inbred strain and was subsequently placed on a B6C3Fe-a/a
(C57BL/6J female × C3HeB/FeJ-a/a male) hybrid background by alter-
nately crossing transplanted ovaries from hyh/hyh females to B6C3Fe F
hybrid males and intercrossing the obligate heterozygous progeny (Bron-
son and Lane 1990). Since the hyh mutation arose on the C57BL/10J
background, the mutation should segregate with the C57BL/10J alleles of
closely linked markers. Therefore, mice from the maintenance cross de-
termined to be heterozygous for C57BL/10J and C3HeB/FeJ-a/a alleles at
the markers D7Mit75, 56, 76, and 57 and determined to be heterozygous
for the hyh mutation were intercrossed to produce the F
progeny or were
mated to the ovary-transplanted hyh/hyh female to produce the backcross
progeny analyzed in this report. Mice were housed and handled in accor-
dance with protocols approved by the IACUC of Harvard Medical School.
Correspondence to: C.A. Walsh; E-mail: email@example.com
*These authors contributed equally to this work.
**Present address: Genome Therapeutics Corporation, 100 Beaver Street,
Waltham, MA 02453-8443, USA.
Mammalian Genome 13, 239–244 (2002).
© Springer-Verlag New York Inc. 2002
Incorporating Mouse Genome