0 3 The the DT 4 10 severe severe JJ 11 20 phenotype phenotype NN 21 23 of of IN 24 31 females female NNS 32 36 with with IN 37 41 tiny tiny JJ 42 46 ring ring NN 47 48 X x NN 49 60 chromosomes chromosome NNS 61 63 is be VBZ 64 74 associated associate VBN 75 79 with with IN 80 89 inability inability NN 90 92 of of IN 93 98 these these DT 99 110 chromosomes chromosome NNS 111 113 to to TO 114 121 undergo undergo VB 122 123 X X NNP 124 136 inactivation inactivation NN 136 137 . . . 139 145 Mental mental JJ 146 157 retardation retardation NN 158 161 and and CC 162 163 a a DT 164 177 constellation constellation NN 178 180 of of IN 181 191 congenital congenital JJ 192 205 malformations malformation NNS 206 209 not not RB 210 217 usually usually RB 218 228 associated associate VBN 229 233 with with IN 234 240 Turner Turner NNP 241 249 syndrome syndrome NN 250 253 are be VBP 254 258 seen see VBN 259 261 in in IN 262 266 some some DT 267 274 females female NNS 275 279 with with IN 280 281 a a DT 282 288 mosaic mosaic JJ 289 303 45,X/46,X,r(X) 45,x/46,x,r(x) NN 304 313 karyotype karyotype NN 313 314 . . . 315 322 Studies study NNS 323 325 of of IN 326 331 these these DT 332 339 females female NNS 340 344 show show VBP 345 349 that that IN 350 353 the the DT 354 358 XIST XIST NNP 359 364 locus locus NN 365 367 on on IN 368 373 their their PRP$ 374 378 tiny tiny JJ 379 383 ring ring NN 384 385 X x NN 386 397 chromosomes chromosome NNS 398 400 is be VBZ 401 407 either either CC 408 411 not not RB 412 419 present present JJ 420 422 or or CC 423 426 not not RB 427 436 expressed express VBN 436 437 . . . 438 440 As as IN 441 445 XIST XIST NNP 446 459 transcription transcription NN 460 462 is be VBZ 463 467 well well RB 468 478 correlated correlate VBN 479 483 with with IN 484 496 inactivation inactivation NN 497 499 of of IN 500 503 the the DT 504 505 X X NNP 506 516 chromosome chromosome NN 517 519 in in IN 520 526 female female JJ 527 534 somatic somatic JJ 535 540 cells cell NNS 541 544 and and CC 545 558 spermatogonia spermatogonia NN 558 559 , , , 560 573 nonexpression nonexpression NN 574 576 of of IN 577 580 the the DT 581 586 locus locus NN 587 591 even even RB 592 596 when when WRB 597 599 it it PRP 600 602 is be VBZ 603 610 present present JJ 611 619 suggests suggest VBZ 620 624 that that IN 625 630 these these DT 631 642 chromosomes chromosome NNS 643 646 are be VBP 647 664 transcriptionally transcriptionally RB 665 671 active active JJ 671 672 . . . 673 675 We we PRP 676 684 examined examine VBD 685 688 the the DT 689 704 transcriptional transcriptional JJ 705 713 activity activity NN 714 716 of of IN 717 721 ring ring NN 722 723 X x NN 724 735 chromosomes chromosome NNS 736 743 lacking lack VBG 744 748 XIST XIST NNP 749 759 expression expression NN 760 761 ( ( ( 761 767 XISTE- XISTE- NNP 767 768 ) ) ) 768 769 , , , 770 774 from from IN 775 780 three three CD 781 788 females female NNS 789 793 with with IN 794 800 severe severe JJ 801 811 phenotypes phenotype NNS 811 812 . . . 813 816 The the DT 817 820 two two CD 821 825 tiny tiny JJ 826 830 ring ring NN 831 832 X x NN 833 844 chromosomes chromosome NNS 845 852 studied study VBN 853 857 with with IN 858 860 an an DT 861 869 antibody antibody NN 870 878 specific specific JJ 879 882 for for IN 883 886 the the DT 887 897 acetylated acetylate VBN 898 906 isoforms isoform NNS 907 909 of of IN 910 917 histone histone NN 918 920 H4 h4 NN 921 928 marking mark VBG 929 940 transcribed transcribe VBN 941 950 chromatin chromatin NN 951 958 domains domain NNS 959 963 were be VBD 964 971 labeled label VBN 972 974 at at IN 975 976 a a DT 977 982 level level NN 983 993 consistent consistent JJ 994 998 with with IN 999 1004 their their PRP$ 1005 1010 being be VBG 1011 1017 active active JJ 1017 1018 . . . 1019 1021 We we PRP 1022 1026 also also RB 1027 1035 examined examine VBD 1036 1039 tow tow NN 1040 1042 of of IN 1043 1046 the the DT 1047 1053 XISTE- xiste- JJ 1054 1058 ring ring NN 1059 1070 chromosomes chromosome NNS 1071 1073 to to TO 1074 1083 determine determine VB 1084 1091 whether whether IN 1092 1097 genes gene NNS 1098 1102 that that WDT 1103 1106 are be VBP 1107 1115 normally normally RB 1116 1122 silent silent JJ 1123 1125 on on IN 1126 1128 an an DT 1129 1137 inactive inactive JJ 1138 1139 X x NN 1140 1143 are be VBP 1144 1153 expressed express VBN 1154 1158 from from IN 1159 1164 these these DT 1165 1176 chromosomes chromosome NNS 1176 1177 . . . 1178 1186 Analyses analysis NNS 1187 1189 of of IN 1190 1196 hybrid hybrid JJ 1197 1202 cells cell NNS 1203 1207 show show VBP 1208 1212 that that IN 1213 1217 TIMP TIMP NNP 1217 1218 , , , 1219 1223 ZXDA ZXDA NNP 1223 1224 , , , 1225 1228 and and CC 1229 1233 ZXDB ZXDB NNP 1234 1238 loci locus NNS 1239 1241 on on IN 1242 1245 the the DT 1246 1254 proximal proximal JJ 1255 1260 short short JJ 1261 1264 arm arm NN 1264 1265 , , , 1266 1269 and and CC 1270 1272 AR AR NNP 1273 1276 and and CC 1277 1282 PHKA1 phka1 NN 1283 1287 loci locus NNS 1288 1290 on on IN 1291 1294 the the DT 1295 1299 long long JJ 1300 1303 arm arm NN 1303 1304 , , , 1305 1308 are be VBP 1309 1313 well well RB 1314 1323 expressed express VBN 1324 1328 from from IN 1329 1332 the the DT 1333 1337 tiny tiny JJ 1338 1342 ring ring NN 1343 1344 X x NN 1345 1355 chromosome chromosome NN 1356 1363 lacking lack VBG 1364 1368 XIST XIST NNP 1369 1372 DNA DNA NNP 1372 1373 . . . 1374 1381 Studies study NNS 1382 1384 of of IN 1385 1388 the the DT 1389 1393 ring ring NN 1394 1404 chromosome chromosome NN 1405 1409 that that WDT 1410 1413 has have VBZ 1414 1418 XIST XIST NNP 1419 1422 DNA DNA NNP 1423 1426 but but CC 1427 1431 does do VBZ 1432 1435 not not RB 1436 1446 transcribe transcribe VB 1447 1449 it it PRP 1450 1454 show show VBP 1455 1459 that that IN 1460 1463 its its PRP$ 1464 1466 AR ar NN 1467 1473 allele allele NN 1474 1476 is be VBZ 1477 1488 transcribed transcribe VBN 1489 1494 along along IN 1495 1499 with with IN 1500 1503 the the DT 1504 1507 one one CD 1508 1510 on on IN 1511 1514 the the DT 1515 1521 normal normal JJ 1522 1523 X x NN 1524 1530 allele allele NN 1530 1531 . . . 1532 1533 ( ( ( 1533 1541 ABSTRACT abstract NN 1542 1551 TRUNCATED truncated VBN 1552 1554 AT at IN 1555 1558 250 250 CD 1559 1564 WORDS words NNS 1564 1565 ) ) )