Syntenic homology of human unique DNA sequences within chromosome regions 5 q 31 , 10 q 22 , 13 q 32-33 and 19 q 13 . 1 in the great apes

Homologies between chromosome banding patterns and DNA sequences in the great apes and humans suggest an apparent common origin for these two lineages. The availability of DNA probes for specific regions of human chromosomes (5q31, 10q22, 13q32-33 and 19q13.1) led us to cross-hybridize these to chimpanzee (Pan troglodytes, PTR), gorilla (Gorilla gorilla, GGO) and orangutan (Pongo pygmaeus, PPY) chromosomes in a search for equivalent regions in the great apes. Positive hybridization signals to the chromosome 5q31-specific DNA probe were observed at HSA 5q31, PTR 4q31, GGO 4q31 and PPY 4q31, while fluorescent signals using the chromosome 10q22-specific DNA probe were noted at HSA 10q22, PTR 8q22, GGO 8q22 and PPY 7q22. The chromosome arms showing hybridization signals to the Quint-Essential 13-specific DNA probe were identified as HSA 13q32-33, PTR 14q32-33, GGO 14q32-33 and PPY 14q32-33, while those presenting hybridization signals to the chromosome 19q13.1-specific DNA probe were identified as HSA 19q13.1, PTR 20q13, GGO 20q13 and PPY 20q13. All four probes presumably hybridized to homologous chromosomal locations in the apes, which suggests a homology of certain unique DNA sequences among hominoid species. Division of Molecular Medicine and Genetics, Wyckoff Heights Medical Center, 374 Stockholm St. Brooklyn, NY 11237, USA. Send correspondence to R.S.V. Fax: +1-718-486-4270. The present address of R.U.V.-S. is Biological Research and Services Laboratory, Natural Sciences Research Institute, University of the Philippines, Diliman, Quezon City, Philippines 1101. 528 Vallente-Samonte et al. The chromosome 5q31-specific DNA probe contains a pool of 15 probes that commonly map to cytogenetic band 5q31 (Oncor, Inc.). The chromosome 10q22-specific DNA probe hybridized to sequences of the HK1 locus of human chromosomes. The Quint-Essential 13-specific DNA probe (D13S585) hybridizes to chromosome bands 13q32-q33. The chromosome 19q13.3-specific DNA probe hybridized to band 19q13.1 of human chromosomes. We compared the hybridization signals of these chromosomespecific DNA probes on great ape metaphase chromosomes. Under the hybridization conditions used, the probes showed equally strong fluorescent signals at homologous positions in ape chromosomes, based on standard nomenclature (ISCN, 1985) (Figure 1). The summary of localization sites using the DNA probes is presented in Table I. Chromosome band 5q31 has been correlated with the gene cluster encoding for the cytokines interleukin-13 (IL13) and interleukin-4 (IL-4) (Dolganov et al., 1996). Deletion of this band has been used frequently in the diagnosis of myeloid disorders (Paietta et al., 1987; Chandrasekharappa et al., 1990), and has been linked to susceptibility genes for bronchial hyperresponsiveness and asthma (Levitt and Holroyd, 1995). Several translocation breakpoints conferring leukemia have also been observed in this region (Sharp et al., 1987; Nakagawa et al., 1991; Knuutila et al., 1993). Chromosome band 10q22 contains the gene cluster encoding glutamate dehydrogenase (Anagnou et al., 1993) and the glycoprotein prosaposin (Bar-Am et al., 1996) and duplications and/or translocations have been reported in this region in humans. The excision repair gene ERCC5 has been localized within bands 13q32-q33 (Takahashi et al., 1992). The mapping of chromosome 13 has recently been completed (Hawthorn et al., 1994). Chromosome band 19q13.1 has been implicated in malignant hyperthermia (McCarthy et al., 1990; Deufel et al., 1995) and autosomal recessive congenital nephrotic syndrome of the Finnish type (CNF) (Mannikko et al., 1995; Fuchshuber et al., 1996). This region also contains the kallikrein gene family, which encodes the prostate-specific antigen (PSA) (Sutherland et al., 1988), and the human brain Na-dependent inorganic phosphate (Pi) cotransporter (hBNPI) (Ni et al., 1996). These findings may serve as phylogenetic parameters in establishing an animal model for human diseases. Figure 1 Hybridization signals on (a) human, (b) chimpanzee, (c) gorilla and (d) orangutan chromosomes using the human chromosome-specific [A] 5q31, [B] 10q22 (HK1), [C] Quint-Essential 13q32-33 (D13S585) and [D] 19q13.1 DNA probes. Table I Summary of localization of chromosome-specific DNA probes in the great ape species. ChromosomeChromosomal assignment specific DNA probe Homo sapiens Pan troglodytes Gorilla gorilla Pongo pygmaeus (HSA) (PTR) (GGO) (PPY) 5q31 5q31 4q31 4q31 4q31 10q22 10q22 8q22 8q22 7q22 Quint-Essential 13q32-33 14q32-q33 14q32-33 14q32-33 13q32-33 19q13.1 19q13.1 20q13 20q13 20q13 a b c d


INTRODUCTION
Cytogenetic findings based on chromosome banding patterns have suggested similarities between great ape and human chromosomes while molecular data has further strengthened the concept of human descent (Luke and Verma, 1995).Fluorescence in situ hybridization (FISH) employing DNA probes has been used to analyze these genomes (Wienberg et al., 1990).Several composite DNA probes delineating chromosomal subregions and gene-specific loci have been constructed.The homology of subchromosomal regions and the reconstruction of intrachromosomal rearrangements in the genomes of closely related species can be achieved by comparative genomic hybridization (Arnold et al., 1996).In the present investigation, the locations of four human chromosome-specific DNA sequences have been identified in the chimpanzee, gorilla and orangutan and provide additional argument for the process of speciation leading to the descent of man.

Chromosome preparation
Metaphase spreads were prepared from fibroblast cell lines of chimpanzee (AGO 6939A, Pan troglodytes, PTR) and orangutan (AGO 5252, Pongo pygmaeus, PPY) obtained from the Coriell Institute for Medical Research, Camden, NY, while a lymphoblast cell line of gorilla (CRL 1854, Gorilla gorilla, GGO) was obtained from the American Type Culture Collection (Rockville, MD, USA).Human chromosomes were prepared from PHA-stimulated lymphocyte cultures obtained from healthy individuals.The cultured cells were harvested using standard protocols (Verma and Babu, 1995).

FISH
The conditions for in situ hybridization were as described by Lichter et al. (1988).Briefly, chromosome preparations were dehydrated through an ethanol series and denatured in 70% formamide in 2X SSC, pH 7.0, at 72 o C. The digoxigenin-labelled DNA probes used were as follows: chromosome 5q31-specific, chromosome 10q22-specific (HK1), Quint-Essential TM chromosome 13-specific (D13S585) and chromosome 19q13.1-specific(Oncor, Gaithersburg, MD, USA).Overnight hybridization was performed at 37 o C. Post-hybridization washes were done using 2X SSPE, pH 7.0, at 70 o C. The probes were detected using fluorescein-labelled digoxigenin.Chromosomes were counterstained with DAPI/antifade and observed under fluorescent optics.Digital images were obtained using a cooled CCD camera (Oncor).

RESULTS AND DISCUSSION
Four chromosome-specific DNA probes were used to search for their equivalent positions in ape chromosomes.Syntenic homology of human unique DNA sequences within chromosome regions 5q31, 10q22, 13q32-33 and 19q13.1 in the great apes Rhea U. Vallente-Samonte, Robert A. Conte and Ram S. Verma

Abstract
Homologies between chromosome banding patterns and DNA sequences in the great apes and humans suggest an apparent common origin for these two lineages.The availability of DNA probes for specific regions of human chromosomes (5q31, 10q22, 13q32-33 and 19q13.1)led us to cross-hybridize these to chimpanzee (Pan troglodytes, PTR), gorilla (Gorilla gorilla, GGO) and orangutan (Pongo pygmaeus, PPY) chromosomes in a search for equivalent regions in the great apes.Positive hybridization signals to the chromosome 5q31-specific DNA probe were observed at HSA 5q31, PTR 4q31, GGO 4q31 and PPY 4q31, while fluorescent signals using the chromosome 10q22-specific DNA probe were noted at HSA 10q22, PTR 8q22, GGO 8q22 and PPY 7q22.The chromosome arms showing hybridization signals to the Quint-Essential TM 13-specific DNA probe were identified as HSA 13q32-33, PTR 14q32-33, GGO 14q32-33 and PPY 14q32-33, while those presenting hybridization signals to the chromosome 19q13.1-specificDNA probe were identified as HSA 19q13.1,PTR 20q13, GGO 20q13 and PPY 20q13.All four probes presumably hybridized to homologous chromosomal locations in the apes, which suggests a homology of certain unique DNA sequences among hominoid species.The chromosome 5q31-specific DNA probe contains a pool of 15 probes that commonly map to cytogenetic band 5q31 (Oncor, Inc.).The chromosome 10q22-specific DNA probe hybridized to sequences of the HK1 locus of human chromosomes.The Quint-Essential TM 13-specific DNA probe (D13S585) hybridizes to chromosome bands 13q32-q33.The chromosome 19q13.3-specificDNA probe hybridized to band 19q13.1 of human chromosomes.We compared the hybridization signals of these chromosomespecific DNA probes on great ape metaphase chromosomes.
Under the hybridization conditions used, the probes showed equally strong fluorescent signals at homologous positions in ape chromosomes, based on standard nomenclature (ISCN, 1985) (Figure 1).The summary of localization sites using the DNA probes is presented in Table I.
Chromosome band 5q31 has been correlated with the gene cluster encoding for the cytokines interleukin-13 (IL-13) and interleukin-4 (IL-4) (Dolganov et al., 1996).Deletion of this band has been used frequently in the diagnosis of myeloid disorders (Paietta et al., 1987;Chandrasekharappa et al., 1990), and has been linked to susceptibility genes for bronchial hyperresponsiveness and asthma (Levitt and Holroyd, 1995).Several translocation breakpoints conferring leukemia have also been observed in this region (Sharp et al., 1987;Nakagawa et al., 1991;Knuutila et al., 1993).Chromosome band 10q22 contains the gene cluster encoding glutamate dehydrogenase (Anagnou et al., 1993) and the glycoprotein prosaposin (Bar-Am et al., 1996) and duplications and/or translocations have been reported in this region in humans.The excision repair gene ERCC5 has been localized within bands 13q32-q33 (Takahashi et al., 1992).The mapping of chromosome 13 has recently been completed (Hawthorn et al., 1994).Chromosome band 19q13.1 has been implicated in malignant hyperthermia (McCarthy et al., 1990;Deufel et al., 1995) and autosomal recessive congenital nephrotic syndrome of the Finnish type (CNF) (Mannikko et al., 1995;Fuchshuber et al., 1996).This region also contains the kallikrein gene family, which encodes the prostate-specific antigen (PSA) (Sutherland et al., 1988), and the human brain Na + -dependent inorganic phosphate (P i ) cotransporter (hBNPI) (Ni et al., 1996).These findings may serve as phylogenetic parameters in establishing an animal model for human diseases.Fluorescence in situ hybridization (FISH) using locispecific probes has been used to identify intrachromosomal changes based on DNA homology and has provided a powerful tool for studying karyological and genomic evolution (Muller et al., 1996).Our observations based on DNA hybridization experiments with great ape chromosomes indicate that a syntenic homology has been preserved in these regions during the course of hominoid differentiation.The presence functionally conserved segments in the corresponding ape chromosomes further supports the concept of evolution at the DNA sequence level.
Division of MolecularMedicine and Genetics, Wyckoff Heights Medical Center, 374 Stockholm St.
Brooklyn, NY 11237, USA.Send correspondence to R.S.V. Fax: +1-718-486-4270.The present address of R.U.V.-S. is Biological Research and Services Laboratory, Natural Sciences Research Institute, University of the Philippines, Diliman, Quezon City, Philippines 1101.

Table I -
Summary of localization of chromosome-specific DNA probes in the great ape species.