Possible inactivation of part of chromosome 13 due to 13qXp translocation associated with retinoblastoma

Chromosome examination of a female patient with 13/X translocation associated with retinoblastoma was carried out using peripheral blood lymphocytes and cultured skin fibroblasts. The constitutional karyotype was 46,X,t(l 3;X) (q12;p22). Q-banding analysis showed that the translocated chromosomes were of paternal origin. Studies on DNA replication pattern with Giemsa banding using the bromodeoxyuridine substitution technique revealed that the derivative X chromosome was late replicating, and the translocated chromosome 13 was affected by the spreading of lyonization. Such a functional monosomy of 13q14 may also be involved in retinal blasts, and be related to the development of retinoblastoma.     

X-inactivation pattern in three cases of X/autosome translocation

We describe an X/15 translocation which was balanced in a phenotypically normal mother [46,X,t(X;15)(p22;q15)] and unbalanced in her phenotypically abnormal daughter [46,X,der(X),t(X;15)(p22;q15)mat]. A third case involves a balanced X/21 translocation in a girl with a multiple congenital anomaly-retardation syndrome [46,X,t(X;21)(p11;p11?)]. 5-BrdU acridine orange banding on lymphocytes revealed late replication of the normal X chromosome in the mother and of the normal or abnormal X chromosome in the two other cases. Our findings are only partially consistent with previous observations. All X-inactivation patterns can be explained by random inactivation and subsequent selection against specific cell lines. Furthermore, the findings in our patient with X/21 translocation support the hypothesis of the existence of one inactivation center on Xq.     

Prenatal evaluation of a de novo X;9 translocation

A case of X-autosome translocation was diagnosed prenatally [46,X,t(X;9)(p21.3∼ 22.1;q22]. We describe the use of fluorescence in situ hybridization (FISH) to estimate the integrity of the Duchenne muscular dystrophy (DMD) gene. X-inactivation studies were used as well to assess the probability of phenotypic abnormalities associated with functional partial disomy X and monosomy 9. Am. J. Med. Genet. 85:476–478, 1999. © 1999 Wiley-Liss, Inc.     

Molecular and cytogenate analysis of an X/autosomal translocation: 45, X, dic(X;17)(p22.2;p13)

We present an unusual case of monosomy 17p13-pter and monosomy Xp22.2-pter due to a dicentric translocation chromosome X/17 in a female newborn with severe anomalies. The karyotype was identified as 45, X, dic(X;17)(p22.2;p13) by high resolution GTG banding in lymphocytes. R banding showed the translocational X-chromosome to be late replicating, and there was no spreading of X-inactivation onto the autosomal segment. Furthermore, it could be demonstrated by C banding that the X-centromere in the translocation chromosome was inactive.
The results of short tandem repeat (STR) typing confirmed the partial monosomy X and 17 as well as the paternal origin of the two chromosomes X and 17 which were involved in the translocation chromosome formation. The cell stage of the structural rearrangement was consistent with paternal meiosis as well as with postzygotic mitosis. The monosomy was confirmed in lymphocytes and fibroblasts, and mosaicism was not detected.     

Tertiary trisomy due to a reciprocal translocation of chromosomes 5 and 21 in a four‐generation family

Tertiary trisomy, or double trisomy, is a rare occurrence. We present two individuals with a previously unreported tertiary trisomy for chromosomes 5p and 21q in an eight‐generation pedigree. Their phenotypes are compared with other partial trisomies of either 5p or 21q from the literature. The propositus was diagnosed with trisomy 21 at 2 years of age after a karyotype study for short stature and developmental delay. His phenotype was described as atypical for Down syndrome. He presented at 9 years of age because of pervasive behavioral problems and obesity. He was brachycephalic with a flattened nasal bridge, but he lacked other characteristics of trisomy 21. Because of lack of phenotypic evidence of Down syndrome, a repeat karyotype was obtained and showed 47,XY,+der(21)t(5;21)(p15.1; q22.1), incorporating partial trisomies of both chromosomes 5 and 21. Mother had a balanced translocation, 46,XX,t(5;21)(p15.1; q22.1); 8 other relatives were examined. The translocation originated from the maternal great‐grandmother, but only the propositus and his mentally retarded aunt had a similar phenotye and the derivative chromosome. Fluorescence in situ hybridization showed absence of band 21q22.2 in the derivative chromosome of the propositus and his aunt, indicating that neither had trisomy for the Down syndrome critical region. These cases represent a unique double partial trisomy of chromosome arms 5p and 21q that occurred because of 3:1 malsegregation of a reciprocal translocation. These cases further demonstrate that phenotypic discordance with cytogenetic results dictate further investigation using advanced cytogenetic hybridization. Am. J. Med. Genet. 92:311–317, 2000. © 2000 Wiley‐Liss, Inc.     

Molecular cytogenetic studies of Xq critical regions in premature ovarian failure patients

BACKGROUND: Premature ovarian failure (POF) is defined as amenorrhoea for more than 6 months, occurring before the age of 40, with an FSH serum level higher than 40 mIU/ml. Cytogenetically visible rearrangements of the X chromosome are associated with POF. Our hypothesis was that cryptic Xq chromosomal rearrangements could be an important etiological contributor of POF. METHODS: Ninety POF women were recruited and compared to 20 control women. Peripheral blood samples were collected and metaphase chromosomes were prepared using standard cytogenetic methods. To detect Xq chromosomal micro-rearrangements, fluorescence in situ hybridization (FISH) analysis was performed using a selection of 30 bacterial artificial chromosome (BAC) and P1 artificial chromosome clones, spanning Xq13-q27. We further localized the translocation breakpoints by FISH with additional BAC clones. RESULTS: Chromosomal abnormalities were identified in 8.8% of our 90 patients [one triple X, three large Xq deletions 46,X,del(X)(q22.3), 46,X,del(X)(q21.2) and 46,X,del(X)(q21.32), two balanced X;autosome translocations 46,X,t(X;1) (q21.1;q32) and 46,X,t(X;9)(q21.31;q21.2) and two Robertsonian translocations 45,XX,der(15;22)(q10;q10) and 45,XX,der(14;21)(q10;q10)]. The two Xq translocation breakpoints were among a cluster of repetitive elements without any known genes. FISH analysis did not reveal any Xq chromosomal micro-rearrangement. CONCLUSIONS: Karyotyping is definitely helpful in the evaluation of POF patients. No submicroscopic chromosomal rearrangements affecting Xq region were identified. Further analysis using DNA microarrays should help delineate Xq regions involved in POF.     

Turner''s syndrome with a duplication-deficiency X chromosome derived from a maternal pericentric inversion X chromosome

A 31-year-old woman of short stature with severe oligomenorrhea was found to carry a duplication-deficiency X chromosome, 46,X,rec(X)dup q,inv(X)(p22q11), inherited from her mother who carried a pericentric inversion X chromosome, 46,X,inv(X)(p22q11). By a combination of autoradiography and BUdR incorporation, the duplication-deficiency X chromosome was always found to be the inactive and late replicating one. In the cultured fibroblasts with the recombinant X chromosome, some of the cells were seen to have bipartite X chromatin bodies. In the mother with inv(X), the normal and the inverted X chromosome were inactivated at random.     

X/autosome translocation in three generations ascertained through an infant with trisomy 16p due to failure of spreading of X-inactivation

We report on a reciprocal translocation t(X;16)(q28;p12) detected in a newborn girl with clinical manifestations of partial trisomy 16p. A balanced translocation was found in the mother and in the maternal grandmother. Replication studies on lymphocytes and fibroblasts showed nonrandom X-inactivation in both the patient and her mother. In the mother, the derivative X (der(X)) was active, whereas the normal X was late replicating. In contrast, in the patient the der(X) was late replicating, and there was no spreading of X-inactivation onto the autosomal segment, thus giving an explanation for the full clinical picture of partial trisomy 16p. © 1996 Wiley-Liss, Inc.     

Spreading of inactivation in an (X;14) translocation

In the KOP translocation, t(X;14) (q13; q32), virtually the entire long arm of the X has been translocated to the end of the long arm of chromosome 14. Meiotic secondary nondisjunction in a female balanced carrier of the translocation has led to a son with two der(14) or 14-X chromosomes. The normal X chromosome is late replicating in the mother. One of the two 14-X Chromosomes is late replicating in the son, with heavy terminal labeling of all but the centromeric end of the chromosome. This suggests that genetic inactivation has spread from the Xq segment of the translocation chromosome to at least two thirds of the segment derived from chromosome 14, and that the remaining proximal segment of chromosome 14 is possibly still genetically active. These findings provide an explanation for the phenotype: Klinefelter syndrome plus a few mild malformations that are sometimes seen in this syndrome but are also seen in duplication of the proximal portion of chromosome 14. Although the proband has a duplication of virtually an entire chromosome 14, 14(pter→q32), the phenotypic effect of the autosomal duplication has been mostly nullified by the spread of inactivation.     

Translocation t(X;21)(q13.3; p11.1) in a girl with Menkes disease

A girl with a 46,X,t(X;21) (q13.3;p11.1) karyotype presented with skin redundancy, especially in the neck, prominent occiput and micrognathia, and later developed hypotonia, hypopigmentation, sparse scalp hair, and profound mental retardation characteristic of Menkes disease. Her serum copper (14 μg/dl) and ceruloplasmin (9 mg/dl) levels were extremely low. Fluorescent in situ hybridization analysis with a 100-kb P1-derived artificial chromosome probe containing the Menkes disease gene demonstrated three twin-signals, one on the normal X chromosome and one each on derivative chromosomes X and 21, indicating that the Xq13.3 breakpoint was located within the gene. Replication pattern analysis showed that the normal X chromosome was late replicating, whereas the derivative X chromosome was selectively early replicating. These results indicated that Menkes disease in our patient resulted from a de novo translocation that disrupts the disease gene. Am. J. Med. Genet. 79:191–194, 1998. © 1998 Wiley-Liss, Inc.     

t(1;18)(q32.1;q22.1) associated with genitourinary malformations

We report a male infant who has impaired penile development, hypospadias, and mild developmental delay with a 46,XY,t(1;18)(q32.1;q22.1) karyotype. Fluorescent in situ hybridization (FISH) was performed to more precisely map the translocation breakpoint. The translocation breakpoint maps to a region that has been implicated in genitourinary malformations in the 18q- syndrome. This case report suggests that a gene involved in genitourinary development maps at or near the chromosome 18 translocation breakpoint.     

Partial trisomy 19p: case report and natural history

Partial trisomy 19p was noted in an infant delivered at 39 weeks gestation with intrauterine growth retardation (IUGR), bilateral club feet, renal abnormalities, hearing deficit, and multiple dysmorphic features. Chromosomes obtained following amniocentesis at 32 weeks gestation revealed that the fetus was partially trisomic for 19p and partially monosomic for a portion of the terminal band of 3q, having inherited a derivative chromosome 3 from her father [46,XX,-3,+der(3)t(3;19)(q29;p13.2)pat]. The father was found to be the carrier of a balanced translocation between chromosomes 3 and 19 [46,XY,t(3;19)(q29;p13.2)]. The only other case of partial trisomy 19p previously reported was an infant with partial trisomy 19p and partial monosomy 13q who died at 59 days of age. This report by Byrne et al. [(Am J Hum Genet 1980: 32:64A] is similar to our case with respect to IUGR, small palpebral fissures, and ear anomalies.     

Replication banding and molecular studies of a mosaic,unbalanced dic(X;15)(xpter→xq26.1::15p11→15qter)

We present a patient with a chromosomal mosaicism involving the X chromosome. One cell line is 45,X and the other has a de novo paternally derived dicentric X;15 translocation. Her karyotype is therefore 45,X/45,X,dic(X;15)(Xpter→Xq26.1: : 15p11→15 qter) based on G-banding. The presence of 2 centromeres on the derivative X was confirmed by fluorescence in situ hybridization (FISH) and a deletion of Xq26.1→qter was confirmed by polymerase chain reaction (PCR) using DXS52 and DXYS154. Replication banding studies indicate that the derivative X is late replicating. Based on these studies, it is unclear whether inactivation has spread to proximal 15q. The patient has a unique phenotype distinct from Ullrich-Turner or Prader-Willi syndromes, but includes ataxia and language delay which are commonly seen in Angelman syndrome. These findings are contrary to those anticipated since deficiency of paternal genes at 15q12 typically leads to Prader-Willi syndrome. Molecular analysis of PCR-based polymorphisms of chromosome 15 and X indicates that uniparental disomy is not present for the X chromosome or chromosome 15 in either cell line. It is hypothesized that her phenotype results from the interaction of the 2 abnormal genotypes. Each abnormality may be diluted by the mosaicism and, in the derivative X line, by the possible variation among cells of inactivation spreading to chromosome 15. © 1995 Wiley-Liss, Inc.     

Short stature in a mother and daughter caused by familial der(X)t(X;X)(p22.1‐3;q26)

Deletions of the terminal Xp regions, including the short‐stature homeobox (SHOX) gene, were described in families with hereditary Turner syndrome and Léri‐Weill syndrome. We report on a 10‐2/12‐year‐old girl and her 37‐year‐old mother with short stature and no other phenotypic symptoms. In the daugther, additional chromosome material was detected in the pseudoautosomal region of one X chromosome (46,X,add(Xp.22.3)) by chromosome banding analysis. The elongation of the X chromosome consisted of Giemsa dark and bright bands with a length one‐fifth of the size of Xp. The karyotype of the mother demonstrated chromosome mosaicism with three cell lines (46,X,add(X)(p22.3) [89]; 45,X [8]; and 47,X,add(X)(p22.3), add(X)(p22.3) [2]). In both daughter and mother, fluorescence in situ hybridization (FISH), together with data from G banding, identified the breakpoints in Xp22.1‐3 and Xq26, resulting in a partial trisomy of the terminal region of Xq (Xq26‐qter) and a monosomy of the pseudoautosomal region (Xp22.3) with the SHOX gene and the proximal region Xp22.1‐3, including the steroidsulfatase gene (STS) and the Kallmann syndrome region. The derivative X chromosome was defined as ish.der(X)t(X;X)(p22.1‐3;q26)(yWXD2540‐, F20cos‐, STS‐, 60C10‐, 959D10‐, 2771+, cos9++). In daughter and mother, the monosomy of region Xp22.1‐3 is compatible with fertility and does not cause any other somatic stigmata of the Turner syndrome or Léri‐Weill syndrome, except for short stature due to monosomy of the SHOX gene. © 2001 Wiley‐Liss, Inc.     

Translocation X;9(q24;q34) in a girl with ovary dysfunction

A balanced de novo translocation X;9(q24;q34) was discovered in a 21-year-old girl with oligomenorrhoea. The structurally normal X was late replicating in all cells. The results indicate that an X chromosome breakpoint at q24 provokes ovary dysfunction.     

Prenatal evaluation of a de novo X;9 translocation.

A case of X-autosome translocation was diagnosed prenatally [46,X, t(X;9)(p21.3 approximately 22.1;q22]. We describe the use of fluorescence in situ hybridization (FISH) to estimate the integrity of the Duchenne muscular dystrophy (DMD) gene. X-inactivation studies were used as well to assess the probability of phenotypic abnormalities associated with functional partial disomy X and monosomy 9.     

Pseudohermaphroditism with clinical features of trisomy 19 in an infant trisomic for parts of chromosomes 16 and 18: 47,XY,der(18),t(16;18)(p12;q11)mat.

The case is presented of an infant who was diagnosed clinically as trisomy 18 with pseudohermaphroditism. Cytogenetic studies revealed an extra chromosome which represented a translocation chromosome derived from a balanced, reciprocal translocation between chromosomes 16 and 18: [der(18),t(16;18)(p12;q11)mat]. The infant's mother and a number of her relatives were found to be translocation carriers: ]46,XX,t(16;18)(p12;q11)].     

Spreading of inactivation in an (X;14) translocation.

In the KOP translocation, t(X;14)(q13;q32), virtually the entire long arm of the X has been translocated to the end of the long arm of chromosome 14. Meiotic secondary nondisjunction in a female balanced carrier of the translocation has led to a son with two der(14) or 14-X chromosomes. The normal X chromosome is late replicating in the mother. One of the two 14-X chromosomes is late replicating in the son, with heavy terminal labeling of all but the centromeric end of the chromosome. This suggests that genetic inactivation has spread from the Xq segment of the translocation chromosome to at least two thirds of the segment derived from chromosome 14, and that the remaining proximal segment of chromosome 14 is possibly still genetically active. These findings provide an explanation for the phenotype: Klinefelter syndrome plus a few mild malformations that are sometimes seen in this syndrome but are also seen in duplication of the proximal portion of chromosome 14. Although the proband has a duplication of virtually an entire chromosome 14, 14(pter leads to q32), the phenotypic effect of the autosomal duplication has been mostly nullified by the spread of inactivation.     

Down''s syndrome phenotype and autosomal gene inactivation in a child with presumed (X;21) de novo translocation.

A 3 1/2-year-old female with clinical features of Down's syndrome was found to have extra chromosome material on the long arm of one of the X chromosomes, 46,XXq+. The parental karyotypes were normal. In the light of the clinical features of the proband an the banding characteristics of the extra chromosome material, the patient was thought to have a de novo (X;21) translocation. The results of late replication studies with BUdR and enzyme superoxide dismutase (SOD) assays in the proband suggest that: (1) the presumed (X;21) translocation chromosome was the late replicating chromosome; (2) the spread of inactivation extended from the Xq segment of the translocation chromosome to the proximal part of the segment derived from chromosome 21, leading to the inactivation of the autosomal gene for enzyme SOD; (3) the remaining distal portion of the (X;21) translocation chromosome, a part of a segment presumably derived from chromosome 21, was spared from the spread of inactivation so that this part was still genetically active and responsible for the Down's phenotype; (4) therefore, the main determinants for a Down's phenotype may be located more distally (q22.2 or q22.3 or both) than the SOD gene (q22.1) on the long arm of chromosome 21.