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Ornithine aminotransferase-related sequences map to two nonadjacent intervals on the human X chromosome short arm
GENOMICS
10,
276-279
(1991)
SHORT COMMUNICATION Ornithine Aminotransferase-Related Sequences Map to Two Nonadjacent Intervals on the Human X Chromosome Short Arm RONALD G. LAFRENIERE,* MICHAEL T. GERAGHTY, t DAVID VALLE, t THOMAS B. SHOWS,* AND HUNTINGTON F. WILLARD* *Department of Genetics, Stanford University, Stanford, California, 94305; tHoward Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; and *Department of Human Genetics, Roswell Park Memorial Institute, Buffalo, New York 74263 Received November 8, 1990
terization of the mouse/human hybrids AHAllA-Bl, A49-5A, A2-4, t75-2ma-lb, A62-IA-4b, L62-3A, DUA-lA, and DUA-1CsAzB have been described elsewhere (Willard and Riordan, 1985; Mahtani and Willard, 1988; Willard et al., 1989; Brown and Willard, 1990; Myerowitz et al., 1985). Mouse/human hybrids A49-5A and L62-3A contain human chromosome 10 in addition to their X component, and thus contain OAT sequences; the other hybrids used do not (V. E. Powers, unpublished observations). The hamster/human hybrid SIN176, containing a deletion from Xp22.1-Xp11.23, was described previously by Ingle et al. (1985). The probe used (huOAT6) was a 2.0-kb human OAT cDNA cloned into the EcoRI site of the pGEM-4 vector (Mitchell et CL, 1988). Southern blot analysis of HindHI-digested human genomic DNA probed with huOAT6 reveals at least 13 fragments, with sizes estimated at 18.4, 12.4, 9.3, 6.3, 5.0, 4.3, 2.5, 1.9, 1.7, 1.6, 1.4, 0.5, and0.3 kb (see Fig. 1). Human and mouse bands were easily distinguishable. Autosomal bands corresponding to the chromosome 10 OAT locus were identified as 9.3,5.0, 1.4,0.5, and 0.3 kb in size by using the hybrid A49-5A, which contains human chromosome 10 but no human X short-arm material (Fig. 1, lane 2). The remaining fragments were present in a human/mouse hybrid containing only the human X chromosome (AHAllA-Bl, Fig. 1, lane 4) and therefore could be assigned to the X chromosome, as expected from previous data (Mitchell et al., 1986; Ramesh et aZ., 1987; Barrett et al., 1987). All the X-linked bands mapped proximal to an Xp21.1 breakpoint and proximal to an Xp11.3 breakpoint (Fig. 1, lanes 5 and 6), but distal to an Xp11.21 breakpoint (lanes 9 and 10). OATL sequences mapped to both sides of an X/15
Using a panel of human/rodent somatic cell hybrids segregating human X/autosome translocations and deletions, we have refined the localization of the X-linked sequences homologous toornithine-&aminotransferase (OAT), thestructural locus for which (OAT) maps to chromosome 10. OATrelated (“-like”) (OATL) sequences mapped to two nonadjacent intervals: OATLl mapped to Xp11.3-~11.23, while OATL2 mapped to Xp11.22-~11.21. X-linked OATLl sequences polymorphic for ScaI and StuI map to the more distal interval in Xpll.S-~11.23. These results should help guide long-range cloning and mapping studies, as well as refine the genetic linkage map in this region of the X chromosome. 0 1991 Academic Press, Inc.
Ornithine-&aminotransferase is a mitochondrial matrix enzyme important in arginine, proline, and ornithine metabolism. Deficiency of this enzyme in humans causes gyrate atrophy, a progressive degeneration of the choroid and retina that leads to blindness (Valle and Simell, 1989). Gyrate atrophy is inherited as an autosomal recessive trait, consistent with the mapping of the functional gene, OAT, to chromosome 10 (O’Donnell et al., 1988). In addition to the autosoma1 gene, sequences homologous to OAT have been found to map to the proximal short arm of the X chromosome (Mitchell et al., 1986; Ramesh et al., 1987; Barrett et al., 1987). We report here a further refinement of the mapping of these X-linked OAT-related (“-like”) sequences using a panel of human/rodent somatic cell hybrids. Physical mapping of OATL sequences was conducted using somatic cell hybrid lines segregating derivative X/autosome translocations and deletions in the region Xp21.1-~11.21. Construction and characOSSS-7543/91$3.00 Copyright 0 1991 by Academic Press, All rights of reproduction in any form
276 Inc. reserved.
SHORT
COMMUNICATION
277
FIG. 1. Physical mapping of OATLI and OATL2 sequences on the short arm of the human X chromosome. Human genomic and human/rodent hybrid DNAs were digested with Hind111 and Southern blot analyzed using the human cDNA huOAT6 probe. Hybrid names are shown at the top. Human X chromosome content for each of the hybrids is A49-5A (XqZZ-Xqter), AHAllA-Bl (entire X only), A2-4 (XpZl.l-Xqter), t75-2ma-lb (Xpll.3-Xqter), DUA-1A (Xpll.PZ-Xqter), DUA-1CsAzB (Xpter-Xpll.22), A62-lA-4b (Xpll.21-Xqter), L62-3A (Xpter-Xpll.Zl), SIN176 (Xpter-Xp22.11::Xpll.23-Xqter). Note that the “DUA” and “62” series of hybrids contain reciprocal products of balanced X/15 and X/17 translocations, respectively. Size estimates (in kb) for human bands detected are given on the left. Bands assigned to OATLl, OATL2, or OAT are shown on the right. CHO, Chinese hamster ovary DNA.
translocation breakpoint at Xp11.22, with Hind111 fragments 12.4, 2.5, 1.9, and 1.7 kb in size clearly mapping distal and a fragment of 18.4 kb mapping proximal to this breakpoint. In addition, three intense Hind111 fragments of 6.3, 4.3, and 1.6 kb mapped to both sides of this breakpoint, being present in both hybrids DUA-1A (containing the der(X) chromosome) and DUA-1CsAzB (containing the der(15) chromosome). Dosage differences between these and other fragments suggest that
there are several copies of the 6.3-, 4.3-, and 1.6-kb fragments on the X. The pattern intensities between bands in DUA-1A (Fig. 1, lane 7) were the same as those in SIN176 (Fig. 1, lane 12), suggesting that no additional OATL sequences were present between the DUA and SIN176 breakpoints. Digestion of these hybrid DNAs with Stul and ScaI supported the same conclusion (data not shown). Taken in total, these results demonstrate that OATL sequences map to two distinct intervals on the short arm of the X chromo-
278
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COMMUNICATION
FIG. 2. Physical mapping of OATLI polymorphic alleles. DNA was digested with ScaI (A) or StuI (B) huOAT6. Polymorphic alleles are designated Al or A2 (for ScaI alleles) and Bl or B2 (for StuI alleles). For three human female DNAs are shown as homozygous or heterozygous for the particular alleles. Absence human/hamster hybrid maps the polymorphic alleles to the OATLI cluster. DNA size markers (in kb) are hamster ovary DNA.
some. These two distinct locations have been designated OATLl (for those sequencesin Xp11.3-~11.23) and OATL2 (for those sequences in Xp11.22-~11.21). The ScaI polymorphism reported previously by Ramesh et al. (1987) was mapped using the same hybrid panel as that described above. Analysis of 84 unrelated individuals (133 X chromosomes total) verified the size and frequency of the polymorphic alleles as Al (6.0 kb) = 0.63 and A2 (4.0 kb) = 0.37 (Fig. 2A). ScaI polymorphic bands mapped proximal to the Xp11.3 breakpoint (data not shown), but were absent from the SIN176 hybrid (Fig. 2A), placing them in the OATLl cluster in the Xp11.3-Xp11.23 interval. Haines et al. (1989) described a StuI polymorphism for OATL sequences. Our analysis of 81 unrelated in-
and Southern blot analyzed with each of the ScaI and StuI RFLPs, of either allele from the SIN176 given to the right. CHO, Chinese
dividuals (128 X chromosomes total) gave the polymorphic allele frequencies as Bl (10 kb) = 0.59 and B2 (9.4 kb) = 0.41 (Fig. 2B). The polymorphic S&I alleles mapped proximal to the Xp11.3 breakpoint, but were absent from the SIN176 hybrid (Fig. 2B), indicating that they map to OATLl, in the same interval as the ScaI polymorphic alleles. Several previous studies have mapped the functional human OAT gene to chromosome 10 and OATrelated sequences to the X chromosome (Ramesh et al., 1987; O’Donnell et al., 1988; Barrett et al., 1987). Although the exact nature of all of the OATL sequences has not yet been determined, it is known that at least some are processed pseudogenes (Looney et aZ., 1987). Long-range cloning and mapping of these
SHORT
COMMUNICATION
D., TROFA~R, J. A., CONNEALLY, P. M., GUSELLA, J. F., AND BREAKFIELD, X. 0. (1989). A genetic linkage map of human Xp. Cytogenet. Cell Genet. 51: 1010 (Abstract).
xp11.4 Xpll.3
-.--_
Xp11.23 xp11.22 xp11.21 xp11.1 Xqll.1 Xqll.2
DXZI
4.
5.
t
xq12
FIG. 3. Summary of physical map of proximal Xp showing the location of OATLl and OATL2 (boxed) in relation to other Xp loci mapped using the same hybrids as those in Refs. (6) and (12). Hybrid breakpoints are shown as dashed arrows. SYP, synaptophysin; TZMP, tissue inhibitor of metahoproteinases.
sequences have been complicated by the number of sequences and their similarity. Resolution of these sequences into two distinct locations, OATLl and OATL2, should facilitate efforts to assign individual clones to one or the other cluster. Both Haines et al. (1989) and Mahtani et al. (1989) have reported genetic linkage maps of Xp using the OATLl ScaI and StuI polymorphisms. Assignment of both of these polymorphisms to OATLl in Xp11.3~11.23 should assist in interpreting recombination data, since the physical location of OATLl constrains certain orders of markers within the proximal short arm. The data reported here, in conjunction with data reported previously by us (Willard et al., 1989; Ozcelik et al., 1990; Brown and Willard, 1990, Mahtani and Willard, 19&U), support the physical order summarized in Fig. 3.
6.
7.
8.
MITCHELL, G. A., LOONEY, J. E., BRODY, L. C., STEEL, G., SUCHANEK, M., ENGELHARDT, J. F., WILLARD, H. F., AND VALLE, D. (1988). Human ornithine-&aminotransferase: cDNA cloning and analysis of the structural gene. J. Biol. Chem. 263: 1428814295.
10.
MYEROWITZ, R., PIEKARZ, R., NEUFELD, E. F., SHOWS, T. B., AND SUZUKI, K. (1985). Human /I-hexosaminidase o-chain: Coding sequence and homology with the b-chain. Proc. Natl. Acad. Sci. USA 82: 7830-7834. O’DONNELL, J. J., VANNAS-SULONEN, K., SHOWS, T. B., AND Cox, D. R. (1988). Gyrate atrophy of the choroid and retina: Assignment of the omithine aminotransferase structural gene to human chromosome 10 and mouse chromosome 7. Am. J. Hum. Genet. 43: 922-928. OZCELIK, T., LAFRENIERE, R. G., ARCHER, B. T., JOHNSTON, P. A., WILLARD, H. F., FRANCKE, U., AND SUDHOF, T. C. (1990). Synaptophysin: Structure of the human gene and assignment to the X chromosome in man and mouse. Am. J. Hum. Genet. 47: 551-561. RAMESH, V., EDDY, R., BRUNS, G. A., SHIH, V. E., SHOWS, T. B., AND GUSELLA, J. F. (1987). Localization of the ornithine aminotransferase gene and related sequences on two human chromosomes. Hum. Genet. 76: 121-126. VALLE, D., AND SIMELL, 0. (1989). The hyperornithinemias. In “The Metabolic Basis of Inherited Disease” (C. R. Striver, A. L. Beaudet, W. S. Sly, and D. Valle, Eds.), pp. 599-627, McGraw-Hill, New York. WILLARD, H. F., DURFY, S. J., MAHTANI, M. M., DORKINS, H., DAVIES, K. E., AND WILLIAMS, B. R. G. (1989). Regional localization of the TIMP gene on the human X chromosome. Hum. Genet. 81: 234-238. WILLARD, H. F., AND RIORDAN, J. R. (1985). Assignment of the gene for myelin proteolipid protein to the X chromosome: Implications for X-linked myelin disorders. Science 230: 940-942.
11.
ACKNOWLEDGMENTS This work was supported by grants from the National Institutes of Health (HG00013 to H.F.W., EY02948 to D.V., and HG00333 to T.B.S.). D.V. is an Investigator in the Howard Hughes Medical Institute.
13.
REFERENCES
14.
2.
3.
BARREN, D. J., BATEMAN, B., SPARK=, R. S., MOHANDAS, T., KLISAK, I., AND INANA, G. (1987). Chromosomal localization of human ornithine aminotransferase gene sequences to lOq26 and Xp11.2. Invest. Ophthulmol. Vis. Sci. 28: 10371042.
15.
BROWN, C. J., AND WILLARD, gene that escapes inactivation short arm: Implications for G-met. 46: 273-279.
16.
HAINES,
J. L., COREY,
H. F. (1990). Localization of a to the X chromosome proximal X inactivation. Am. J. Hum.
T., OZELIUS,
L., TANZI,
R. E., ZUCKER,
INGLE, C., WILLIAMSON, R., CHAPELLE, A. DE LA, HERVO, R. R., HAAPALA, K., BATES, G., WILLARD, H., PEARSON, P., AND DAVIES, K. E. (1985). Mapping DNA sequences in a human X-chromosome deletion which extends across the region of the Duchenne muscular dystrophy mutation. Am. J. Hum. Genet. 37: 451-463. LOONEY, J., MITCHELL, G., BRODY, L., SUCHANEK, M., STEEL, G., WILLARD, H., AND VALLE, D. (1987). Omithine aminotransferase (OAT) hybridizing regions on the X chromosome: Integration of at least one processed gene on the X and subsequent genomic duplication has generated multiple OAT-hybridizing fragments. Am. J. Hum. Genet. 41: A226 (Abstract). MAHTANI, M. M., AND WILLARD, H. F. (1988). A primary genetic map of the pericentromeric region of the human X chromosome. Genomics 2: 294-301. MAHTANI, M. M., LAFRENIERE, R. G., BROWN, C. J., KRUSE, T. A., AND WILLARD, H. F. (1989). Genetic linkage analysis of nine loci in the pericentromeric region of the human X chromosome. Cytogenet. Cell Genet. 51: 1038 (Abstract). MITCHELL, G., VALLE, D., WILLARD, H., STEEL, G., SuCHANEK, M., AND BRODY, L. (1986). Human ornithine-6aminotransferase (OAT): Cross-hybridizing fragments mapped to chromosome 10 and Xpll.l-21.1. Am. J. Hum. Genet. 39: Al63 (Abstract).
9.
12.
1.
279
10,
276-279
(1991)
SHORT COMMUNICATION Ornithine Aminotransferase-Related Sequences Map to Two Nonadjacent Intervals on the Human X Chromosome Short Arm RONALD G. LAFRENIERE,* MICHAEL T. GERAGHTY, t DAVID VALLE, t THOMAS B. SHOWS,* AND HUNTINGTON F. WILLARD* *Department of Genetics, Stanford University, Stanford, California, 94305; tHoward Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; and *Department of Human Genetics, Roswell Park Memorial Institute, Buffalo, New York 74263 Received November 8, 1990
terization of the mouse/human hybrids AHAllA-Bl, A49-5A, A2-4, t75-2ma-lb, A62-IA-4b, L62-3A, DUA-lA, and DUA-1CsAzB have been described elsewhere (Willard and Riordan, 1985; Mahtani and Willard, 1988; Willard et al., 1989; Brown and Willard, 1990; Myerowitz et al., 1985). Mouse/human hybrids A49-5A and L62-3A contain human chromosome 10 in addition to their X component, and thus contain OAT sequences; the other hybrids used do not (V. E. Powers, unpublished observations). The hamster/human hybrid SIN176, containing a deletion from Xp22.1-Xp11.23, was described previously by Ingle et al. (1985). The probe used (huOAT6) was a 2.0-kb human OAT cDNA cloned into the EcoRI site of the pGEM-4 vector (Mitchell et CL, 1988). Southern blot analysis of HindHI-digested human genomic DNA probed with huOAT6 reveals at least 13 fragments, with sizes estimated at 18.4, 12.4, 9.3, 6.3, 5.0, 4.3, 2.5, 1.9, 1.7, 1.6, 1.4, 0.5, and0.3 kb (see Fig. 1). Human and mouse bands were easily distinguishable. Autosomal bands corresponding to the chromosome 10 OAT locus were identified as 9.3,5.0, 1.4,0.5, and 0.3 kb in size by using the hybrid A49-5A, which contains human chromosome 10 but no human X short-arm material (Fig. 1, lane 2). The remaining fragments were present in a human/mouse hybrid containing only the human X chromosome (AHAllA-Bl, Fig. 1, lane 4) and therefore could be assigned to the X chromosome, as expected from previous data (Mitchell et al., 1986; Ramesh et aZ., 1987; Barrett et al., 1987). All the X-linked bands mapped proximal to an Xp21.1 breakpoint and proximal to an Xp11.3 breakpoint (Fig. 1, lanes 5 and 6), but distal to an Xp11.21 breakpoint (lanes 9 and 10). OATL sequences mapped to both sides of an X/15
Using a panel of human/rodent somatic cell hybrids segregating human X/autosome translocations and deletions, we have refined the localization of the X-linked sequences homologous toornithine-&aminotransferase (OAT), thestructural locus for which (OAT) maps to chromosome 10. OATrelated (“-like”) (OATL) sequences mapped to two nonadjacent intervals: OATLl mapped to Xp11.3-~11.23, while OATL2 mapped to Xp11.22-~11.21. X-linked OATLl sequences polymorphic for ScaI and StuI map to the more distal interval in Xpll.S-~11.23. These results should help guide long-range cloning and mapping studies, as well as refine the genetic linkage map in this region of the X chromosome. 0 1991 Academic Press, Inc.
Ornithine-&aminotransferase is a mitochondrial matrix enzyme important in arginine, proline, and ornithine metabolism. Deficiency of this enzyme in humans causes gyrate atrophy, a progressive degeneration of the choroid and retina that leads to blindness (Valle and Simell, 1989). Gyrate atrophy is inherited as an autosomal recessive trait, consistent with the mapping of the functional gene, OAT, to chromosome 10 (O’Donnell et al., 1988). In addition to the autosoma1 gene, sequences homologous to OAT have been found to map to the proximal short arm of the X chromosome (Mitchell et al., 1986; Ramesh et al., 1987; Barrett et al., 1987). We report here a further refinement of the mapping of these X-linked OAT-related (“-like”) sequences using a panel of human/rodent somatic cell hybrids. Physical mapping of OATL sequences was conducted using somatic cell hybrid lines segregating derivative X/autosome translocations and deletions in the region Xp21.1-~11.21. Construction and characOSSS-7543/91$3.00 Copyright 0 1991 by Academic Press, All rights of reproduction in any form
276 Inc. reserved.
SHORT
COMMUNICATION
277
FIG. 1. Physical mapping of OATLI and OATL2 sequences on the short arm of the human X chromosome. Human genomic and human/rodent hybrid DNAs were digested with Hind111 and Southern blot analyzed using the human cDNA huOAT6 probe. Hybrid names are shown at the top. Human X chromosome content for each of the hybrids is A49-5A (XqZZ-Xqter), AHAllA-Bl (entire X only), A2-4 (XpZl.l-Xqter), t75-2ma-lb (Xpll.3-Xqter), DUA-1A (Xpll.PZ-Xqter), DUA-1CsAzB (Xpter-Xpll.22), A62-lA-4b (Xpll.21-Xqter), L62-3A (Xpter-Xpll.Zl), SIN176 (Xpter-Xp22.11::Xpll.23-Xqter). Note that the “DUA” and “62” series of hybrids contain reciprocal products of balanced X/15 and X/17 translocations, respectively. Size estimates (in kb) for human bands detected are given on the left. Bands assigned to OATLl, OATL2, or OAT are shown on the right. CHO, Chinese hamster ovary DNA.
translocation breakpoint at Xp11.22, with Hind111 fragments 12.4, 2.5, 1.9, and 1.7 kb in size clearly mapping distal and a fragment of 18.4 kb mapping proximal to this breakpoint. In addition, three intense Hind111 fragments of 6.3, 4.3, and 1.6 kb mapped to both sides of this breakpoint, being present in both hybrids DUA-1A (containing the der(X) chromosome) and DUA-1CsAzB (containing the der(15) chromosome). Dosage differences between these and other fragments suggest that
there are several copies of the 6.3-, 4.3-, and 1.6-kb fragments on the X. The pattern intensities between bands in DUA-1A (Fig. 1, lane 7) were the same as those in SIN176 (Fig. 1, lane 12), suggesting that no additional OATL sequences were present between the DUA and SIN176 breakpoints. Digestion of these hybrid DNAs with Stul and ScaI supported the same conclusion (data not shown). Taken in total, these results demonstrate that OATL sequences map to two distinct intervals on the short arm of the X chromo-
278
SHORT
COMMUNICATION
FIG. 2. Physical mapping of OATLI polymorphic alleles. DNA was digested with ScaI (A) or StuI (B) huOAT6. Polymorphic alleles are designated Al or A2 (for ScaI alleles) and Bl or B2 (for StuI alleles). For three human female DNAs are shown as homozygous or heterozygous for the particular alleles. Absence human/hamster hybrid maps the polymorphic alleles to the OATLI cluster. DNA size markers (in kb) are hamster ovary DNA.
some. These two distinct locations have been designated OATLl (for those sequencesin Xp11.3-~11.23) and OATL2 (for those sequences in Xp11.22-~11.21). The ScaI polymorphism reported previously by Ramesh et al. (1987) was mapped using the same hybrid panel as that described above. Analysis of 84 unrelated individuals (133 X chromosomes total) verified the size and frequency of the polymorphic alleles as Al (6.0 kb) = 0.63 and A2 (4.0 kb) = 0.37 (Fig. 2A). ScaI polymorphic bands mapped proximal to the Xp11.3 breakpoint (data not shown), but were absent from the SIN176 hybrid (Fig. 2A), placing them in the OATLl cluster in the Xp11.3-Xp11.23 interval. Haines et al. (1989) described a StuI polymorphism for OATL sequences. Our analysis of 81 unrelated in-
and Southern blot analyzed with each of the ScaI and StuI RFLPs, of either allele from the SIN176 given to the right. CHO, Chinese
dividuals (128 X chromosomes total) gave the polymorphic allele frequencies as Bl (10 kb) = 0.59 and B2 (9.4 kb) = 0.41 (Fig. 2B). The polymorphic S&I alleles mapped proximal to the Xp11.3 breakpoint, but were absent from the SIN176 hybrid (Fig. 2B), indicating that they map to OATLl, in the same interval as the ScaI polymorphic alleles. Several previous studies have mapped the functional human OAT gene to chromosome 10 and OATrelated sequences to the X chromosome (Ramesh et al., 1987; O’Donnell et al., 1988; Barrett et al., 1987). Although the exact nature of all of the OATL sequences has not yet been determined, it is known that at least some are processed pseudogenes (Looney et aZ., 1987). Long-range cloning and mapping of these
SHORT
COMMUNICATION
D., TROFA~R, J. A., CONNEALLY, P. M., GUSELLA, J. F., AND BREAKFIELD, X. 0. (1989). A genetic linkage map of human Xp. Cytogenet. Cell Genet. 51: 1010 (Abstract).
xp11.4 Xpll.3
-.--_
Xp11.23 xp11.22 xp11.21 xp11.1 Xqll.1 Xqll.2
DXZI
4.
5.
t
xq12
FIG. 3. Summary of physical map of proximal Xp showing the location of OATLl and OATL2 (boxed) in relation to other Xp loci mapped using the same hybrids as those in Refs. (6) and (12). Hybrid breakpoints are shown as dashed arrows. SYP, synaptophysin; TZMP, tissue inhibitor of metahoproteinases.
sequences have been complicated by the number of sequences and their similarity. Resolution of these sequences into two distinct locations, OATLl and OATL2, should facilitate efforts to assign individual clones to one or the other cluster. Both Haines et al. (1989) and Mahtani et al. (1989) have reported genetic linkage maps of Xp using the OATLl ScaI and StuI polymorphisms. Assignment of both of these polymorphisms to OATLl in Xp11.3~11.23 should assist in interpreting recombination data, since the physical location of OATLl constrains certain orders of markers within the proximal short arm. The data reported here, in conjunction with data reported previously by us (Willard et al., 1989; Ozcelik et al., 1990; Brown and Willard, 1990, Mahtani and Willard, 19&U), support the physical order summarized in Fig. 3.
6.
7.
8.
MITCHELL, G. A., LOONEY, J. E., BRODY, L. C., STEEL, G., SUCHANEK, M., ENGELHARDT, J. F., WILLARD, H. F., AND VALLE, D. (1988). Human ornithine-&aminotransferase: cDNA cloning and analysis of the structural gene. J. Biol. Chem. 263: 1428814295.
10.
MYEROWITZ, R., PIEKARZ, R., NEUFELD, E. F., SHOWS, T. B., AND SUZUKI, K. (1985). Human /I-hexosaminidase o-chain: Coding sequence and homology with the b-chain. Proc. Natl. Acad. Sci. USA 82: 7830-7834. O’DONNELL, J. J., VANNAS-SULONEN, K., SHOWS, T. B., AND Cox, D. R. (1988). Gyrate atrophy of the choroid and retina: Assignment of the omithine aminotransferase structural gene to human chromosome 10 and mouse chromosome 7. Am. J. Hum. Genet. 43: 922-928. OZCELIK, T., LAFRENIERE, R. G., ARCHER, B. T., JOHNSTON, P. A., WILLARD, H. F., FRANCKE, U., AND SUDHOF, T. C. (1990). Synaptophysin: Structure of the human gene and assignment to the X chromosome in man and mouse. Am. J. Hum. Genet. 47: 551-561. RAMESH, V., EDDY, R., BRUNS, G. A., SHIH, V. E., SHOWS, T. B., AND GUSELLA, J. F. (1987). Localization of the ornithine aminotransferase gene and related sequences on two human chromosomes. Hum. Genet. 76: 121-126. VALLE, D., AND SIMELL, 0. (1989). The hyperornithinemias. In “The Metabolic Basis of Inherited Disease” (C. R. Striver, A. L. Beaudet, W. S. Sly, and D. Valle, Eds.), pp. 599-627, McGraw-Hill, New York. WILLARD, H. F., DURFY, S. J., MAHTANI, M. M., DORKINS, H., DAVIES, K. E., AND WILLIAMS, B. R. G. (1989). Regional localization of the TIMP gene on the human X chromosome. Hum. Genet. 81: 234-238. WILLARD, H. F., AND RIORDAN, J. R. (1985). Assignment of the gene for myelin proteolipid protein to the X chromosome: Implications for X-linked myelin disorders. Science 230: 940-942.
11.
ACKNOWLEDGMENTS This work was supported by grants from the National Institutes of Health (HG00013 to H.F.W., EY02948 to D.V., and HG00333 to T.B.S.). D.V. is an Investigator in the Howard Hughes Medical Institute.
13.
REFERENCES
14.
2.
3.
BARREN, D. J., BATEMAN, B., SPARK=, R. S., MOHANDAS, T., KLISAK, I., AND INANA, G. (1987). Chromosomal localization of human ornithine aminotransferase gene sequences to lOq26 and Xp11.2. Invest. Ophthulmol. Vis. Sci. 28: 10371042.
15.
BROWN, C. J., AND WILLARD, gene that escapes inactivation short arm: Implications for G-met. 46: 273-279.
16.
HAINES,
J. L., COREY,
H. F. (1990). Localization of a to the X chromosome proximal X inactivation. Am. J. Hum.
T., OZELIUS,
L., TANZI,
R. E., ZUCKER,
INGLE, C., WILLIAMSON, R., CHAPELLE, A. DE LA, HERVO, R. R., HAAPALA, K., BATES, G., WILLARD, H., PEARSON, P., AND DAVIES, K. E. (1985). Mapping DNA sequences in a human X-chromosome deletion which extends across the region of the Duchenne muscular dystrophy mutation. Am. J. Hum. Genet. 37: 451-463. LOONEY, J., MITCHELL, G., BRODY, L., SUCHANEK, M., STEEL, G., WILLARD, H., AND VALLE, D. (1987). Omithine aminotransferase (OAT) hybridizing regions on the X chromosome: Integration of at least one processed gene on the X and subsequent genomic duplication has generated multiple OAT-hybridizing fragments. Am. J. Hum. Genet. 41: A226 (Abstract). MAHTANI, M. M., AND WILLARD, H. F. (1988). A primary genetic map of the pericentromeric region of the human X chromosome. Genomics 2: 294-301. MAHTANI, M. M., LAFRENIERE, R. G., BROWN, C. J., KRUSE, T. A., AND WILLARD, H. F. (1989). Genetic linkage analysis of nine loci in the pericentromeric region of the human X chromosome. Cytogenet. Cell Genet. 51: 1038 (Abstract). MITCHELL, G., VALLE, D., WILLARD, H., STEEL, G., SuCHANEK, M., AND BRODY, L. (1986). Human ornithine-6aminotransferase (OAT): Cross-hybridizing fragments mapped to chromosome 10 and Xpll.l-21.1. Am. J. Hum. Genet. 39: Al63 (Abstract).
9.
12.
1.
279