Inherited pericentric inversion of chromosome no. 2 with Robertsonian translocation (13q 14q) resulting in trisomy for chromosome 13q

This report includes a patient with an inherited pericentric inversion of chromosome No. 2 in addition to a Robertsonian translocation resulting in trisomy for chromosome 13q. The chromosomal constitution of the proband was 46,XX,inv(2) (pter leads to p11 : : q14 leads to p11 : : q14 leads to qter); t(13,14) (13qter leads to 13p11 : : 14q11 leads to 14qter). Sequential QFQ, RFA and GTG banding techniques were employed on the chromosomes of all family members. The chromosomal constitutions of the father and his first child were normal while the mother had an inversion of chromosome No. 2 [46,XX,inv(2) (pter leads to p11 : : q14 leads to p11 : : q14 leads to qter)]. The proband inherited this abnormal chromosome. In addition, she had a de novo Robertsonian translocation involving chromosomes 13q and 14q resulting in trisomy of chromosome 13q.     

Two complementary recombinant chromosomes 5 in a healthy woman

We report a healthy woman with two abortions who is a carrier for a rare heterozygous double recombinant of an inv(5) chromosome, karyotype 46,XX,rec(5)dup(5p) inv(5)(p13q22),rec(5)dup(5q)inv(5)(p13q22). Her father had a 46,XY,inv(5)(p13q22) karyotype; his consanguineous wife had died. Molecular investigation of 11 highly polymorphic markers spanning chromosome 5 revealed biparental inheritance for two markers (D5S406, D5S681) on 5p15.3 and 5q13.1, and an allele constellation not compatible with paternal heterodisomy for marker D5S623 on 5q11.2. Eight markers were not informative. Three mechanisms of formation are proposed: First, fertilization of a normal oocyte by a sperm carrying the two recombinant chromosomes 5, followed by postzygotic recombination between the normal maternal homologue and the rec(5)dup(5p), and by loss of the mitotically recombined maternal homologue, leading to segmental paternal heterodisomy 5q13-->qter (trisomic rescue). Second, postzygotic recombination in a 46,XX,inv(5)(p13q22) zygote resulting in the 46,XX,rec(5)dup(5p)inv(5)(p13q22),rec(5) dup(5q)inv(5)(p13q22) karyotype, followed by absence of the original cell line in lymphocytes. Third and most likely, both parents were inv(5) carriers and complementary recombinations in maternal and paternal meiosis resulted in a zygote with two recombinant chromosomes 5. Our patient refused any further studies but later reported the birth of a phenotypically normal child. This is the first report known to us of complementation by two non-homologous recombinant chromosomes in a phenotypically normal woman, and the first example of a child born to a carrier of complementary recombinant chromosomes.     

The variant inv(2)(p11.2q13) is a genuinely recurrent rearrangement but displays some breakpoint heterogeneity

Human chromosome 2 contains large blocks of segmental duplications (SDs), both within and between proximal 2p and proximal 2q, and these may contribute to the frequency of the common variant inversion inv(2)(p11.2q13). Despite their being cytogenetically homogeneous, we have identified four different breakpoint combinations by fluorescence in situ hybridization mapping of 40 cases of inv(2)(p11.2q13) of European origin. For the vast majority of inversions (35/40), the breakpoints fell within the same spanning BACs, which hybridized to both 2p11.2 and 2q13 on the normal and inverted homologues. Sequence analysis revealed that these BACs contain a significant proportion of intrachromosomal SDs with sequence homology to the reciprocal breakpoint region. In contrast, BACs spanning the rare breakpoint combinations contain fewer SDs and with sequence homology only to the same chromosome arm. Using haplotype analysis, we identified a number of related family subgroups with identical or very closely related haplotypes. However, the majority of cases were not related, demonstrating for the first time that the inv(2)(p11.2q13) is a truly recurrent rearrangement. Therefore, there are three explanations to account for the frequent observation of the inv(2)(p11.2q13): the majority have arisen independently in different ancestors, while a minority either have been transmitted from a common founder or have different breakpoints at the molecular cytogenetic level.     

Pericentric inversions of chromosome number 9: benign or harmful?

Pericentric inversions of chromosome number 9 have been studied in 4 different probands: a normal female with designation 46,XX,inv(9)(p12q13); a male with Down syndrome designated as 47,XY,+21,inv(9))p13q13); a premature infant with multiple, congenital malformations who was 46,XX,inv(9)(p12q21), and a Down syndrome proband with 47,XYqs,+21,inv(9)(p13q21). All 4 cases were shown to be inherited based on family studies. These families are discussed with reference to the literature as to what possible effect this structural change could have on the reproductive capability of a normal carrier and what guidelines are available for counseling such a carrier.     

Recombinant chromosome as a result of pericentric inversion of X chromosome

Summary A structural X chromosome abnormality was found in the karyotype of a tall patient with gonadal dysgenesis and with no extragenital anomalies. Based on her mother's karyotype, which showed a pericentric inversion of the X chromosome: 46,X,inv(X)(p22q24), as well as from G and R banding, we concluded that the abnormal X chromosome of our patient was a recombinant chromosome that had originated as a result of one crossing over in the inversion loop during gametogenesis in her mother. The recombinant X chromosome had a partial deletion of Xq and a partial duplication of Xp: 46,X,rec(X),dup p,inv(X)(p22q24). After BUDR incorporation, the abnormal X chromosome of the patient and that of her mother showed a late replication. The karyotype-phenotype correlation and the nonrandom inactivation of the inverted X chromosome in the mother are discussed.     

Genetic analysis of meiotic recombination in humans by use of sperm typing: reduced recombination within a heterozygous paracentric inversion of chromosome 9q32-q34.3.

To investigate patterns of genetic recombination within a heterozygous paracentric inversion of chromosome 9 (46XY inv[9] [q32q34.3]), we performed sperm typing using a series of polymorphic microsatellite markers spanning the inversion region. For comparison, two donors with cytogenetically normal chromosomes 9, one of whom was heterozygous for a pericentric chromosome 2 inversion (46XY inv[2] [p11q13]), were also tested. Linkage analysis was performed by use of the multilocus linkage-analysis program SPERM, and also CRI-MAP, which was adapted for sperm-typing data. Analysis of the controls generated a marker order in agreement with previously published data and revealed no significant interchromosomal effects of the inv(2) on recombination on chromosome 9. FISH employing cosmids containing appropriate chromosome 9 markers was used to localize the inversion breakpoint of inv(9). Analysis of inv(9) sperm was performed by use of a set of microsatellite markers that mapped centromeric to, telomeric to, and within the inversion breakpoints. Three distinct patterns of recombination across the region were observed. Proximal to the centromeric breakpoint, recombination was similar to normal levels. Distal to the telomeric breakpoint, there was an increase in recombination found in the inversion patient. Finally, within the inversion, recombination was dramatically reduced, but several apparent double recombinants were found. A putative model explaining these data is proposed.     

Pericentric inversion in chromosome 2 without phenotypic effect

A subject with pericentric inversion of chromosome 2: 46, XY, inv(2) (p11q13) is described. All the family members which present the same inversion are clinically normal     

Familial pericentric inversion of the X chromosome [inv(X)(p11q28)]

A familial pericentric inversion of the X chromosome [46,X,inv(X)(p11q28)] and [46,inv(X)(p11q28), Y] is reported. The carriers of the inv(X) presented no clinical symptoms. Either the inverted or the normal X chromosome may be late replicating.     

Inv(10)(p11.2q21.2), a variant chromosome

We present 33 families in which a pericentric inversion of chromosome 10 is segregating. In addition, we summarise the data on 32 families in which an apparently identical inv(10) has been reported in the literature. Ascertainment was through prenatal diagnosis or with a normal phenotype in 21/33 families. In the other 12 families, probands were ascertained through a wide variety of referral reasons but in all but one case (a stillbirth), studies of the family showed that the reason for referral was unrelated to the chromosome abnormality. There has been, to our knowledge, no recorded instance of a recombinant chromosome 10 arising from this inversion and no excess of infertility or spontaneous abortion among carriers of either sex. We propose that inv(10)(p11.2q21.2) can be regarded as a variant analogous to the pericentric inversion of chromosome 2(p11q13). We conclude that prenatal chromosome analysis is not justified for inv(10) carriers. In addition, family investigation of carrier status is not warranted in view of the unnecessary concern this may cause parents and other family members. Received: 7 July 1997 / Accepted: 4 August 1997     

Distal 9q trisomy phenotype in a patient with a supernumerary rearranged chromosome [t(X:9)] (author's transl)]

A child with clinical features associated a trisomy for the distal part of 9q was shown to have the following abnormal chromosome complement : 47,XY,+t)X;9) (Xpter yields Xq24:9q31 yields 9qter), inv 9(p11q13), var 14 (14pQFQ34).     

A cytogenetic survey of 200 unclassifiable mentally retarded children with congenital anomalies and 200 normal controls

Summary A cytogenetic survey was carried out on 200 patients with mental retardation and multiple congenital anomalies, and on 200 normal adult controls. Patients with a known syndrome were excluded from the survey. Chromosome analyses were carried out on blind-coded slides using the ASG banding technique as the routine stain. After the initial analyses (at least 15 cells per person) the slides were decoded, destained and reused for C and Q band polymorphism studies.Five major chromosome abnormalities were detected in the patient group during the survey. They included three patients with de novo, apparently balanced, reciprocal translocations, karyotypes 46,XY,rcp(3;16)(q21;p12); 46,XX,rcp(5;8)(p15;q22); and 46,XX,rcp(5;12)(p11;q24); one with karyotype 47,XX,+mar and one with karyotype 46,XX,der(13),t(13;?)(q34;?). One additional patient whose karyotype in lymphocytes was 46,XX,inv(9)(p11;q13) was found to have a mosaic karyotype 46,XX,inv(9)(p11;q13)/46,XX,inv(9) (p11;q13),der(12),t(12;?)(p13;?) in cultured skin fibroblasts. None of the 200 controls had a major chromosome abnormality.From the combined results of this and previous surveys it is now apparent that about 6.2% of the unclassifiable mentally retarded patients with three or more congenital anomalies and about 0.7% of the controls reveal major chromosome abnormalities.     

Molecular cytogenetic identification and characterization of a de novo supernumerary neocentromeric derivative chromosome 13

We report a young girl with microphthalmia, conductive deafness, aortic isthmus stenosis, laryngomalacia, and laryngeal stenosis carrying a de novo supernumerary neocentromeric derivative chromosome 13. For the precise identification and characterization of the eu- and heterochromatic content of the marker chromosome, straightforward molecular cytogenetic analyses were performed, such as chromosome microdissection, FISH with different probes (e.g. wcp, alphoid centromeric probes, BAC), centromere-specific multicolor FISH (cenM-FISH), and multicolor banding (MCB). The analyses demonstrated that the marker consisted of an inverted duplication (partial tetrasomy) of the distal portion of chromosome 13 that was separated from the endogenous chromosome 13 centromere. Using an all-centromere probe and multicolor cenM-FISH, no alpha-satellite DNA hybridization signal was detectable on any portion of the derivative chromosome. The presence of a functional and active neocentromere on the derivative chromosome 13 was confirmed by positive immunofluorescence signals with CENP-C antibodies. BAC-FISH confirmed the cytogenetic localization of the neocentromere in band 13q31.3. Thus the patient had a mosaic conventional karyotype mos 47,XX,+inv dup(13)(qter-->q21.3::q21.3-->q31.3-->neo-->q31.3-->qter)[6]/46,XX [49].     

Detection of an unbalanced t(4;15) by FISH in a child with multiple congenital anomalies

Detection of an unbalanced t(4;15) by FISH in a child with multiple congenital anomalies: In this report, we present the clinical history and findings in a 6-month-old male with multiple congenital anomalies, developmental delay, and an initial male karyotype with 4q+. The origin of the additional segment on 4q was unequivocally established by fluorescence in situ hybridization (FISH). Whole chromosome probe for chromosome 4 and chromosome 15-specific a-satellite probe were used. The karyotype was demonstrated to be 46,XY,der(4), t(4;15)(q35;?),inv(9)(p13q13). To the best of our knowledge the above cytogenetic abnormalities with these clinical findings have not been described previously. This case further demonstrates the advantage of FISH in the identification of anomalous chromosome regions and breakpoints.     

Human T-cell tumours containing chromosome 14 inversion or translocation with breakpoints proximal to immunoglobulin joining regions at 14q32.

T-cell tumours are frequently found to carry an inversion of chromosome 14 (inv(14)) (q11;q32) or more rarely a chromosome 14 translocation t(14;14) with the same cytogenetic breakpoints (q11;q32). We have examined the molecular junctions of an inv(14) and a translocation t(14;14) using T-cell receptor (TCR) alpha joining (J) region probes. Both of these chromosomal abnormalities have breakpoints within the TCR J alpha locus at 14q11 and both have breakpoints which are proximal (i.e. on the centromeric side) to the immunoglobulin heavy chain JH region at 14q32. The cloned segments corresponding to the junctions at 14q32 are not associated with obvious immunoglobulin-like sequences. This contrasts to the previously described inv(14) in the cell line SUP-T1 and places a potential cluster of chromosome 14 breakpoints downstream of the Ig JH locus. The possible role of the varying breakpoints in the development of these tumours is discussed.     

Pericentric inversions of chromosome 12 in two families

Summary Two cases of pericentric inversion of chromosome 12 are presented, one 46,XX,inv(12)(p13;q11) and the other 47,XX,+21,inv(12)(p13;q13). In both cases one of the parents was also a heterozygotic carrier of the inversion. These inversions were detected among 4035 cytogenetic analyses carried out in patients with psychosomatic retardation and/or malformations (357 with a Down phenotype) and in patients with histories of miscarriages, sterility, or growth failure.In cases studied from a review of the literature together with our own we found that among 3235 cases of Down syndrome there were 7 patients with trisomy 21 and inherited balanced reciprocal translocation involving chromosomes other than pair 21. The frequent participation of some chromosomes in these balanced reciprocal translocations, above all those of group A (1–3), suggests that these and probably other rearrangements could make the segregation of chromosome 21 easier.     

A dysmorphic newborn with 45,X,der(1)inv(1)(p13;qter)t(Y;1)(pter-->q11;p13),-Y de novo karyotype

A dysmorphic newborn with 45,x,der(1)inv(1)(p13;qter)t(y;1)(pter-->q11;p13),-Y de novo karyotype: Y/autosome translocations are very rare chromosomal rearrangements. In most cases, the long arm of the Y chromosome is translocated onto an autosome and most patients are referred because of male infertility. Y/1 translocations are very rare, and have been reported in seven patients so far. Pericentric inversions may be seen in all chromosomes and are not associated with phenotypic abnormalities. Here we report a 6-day old male baby with prenatal growth retardation, frontal bossing, hypertelorism, micrognathia, cleft soft palate, absent uvula, hypospadias, simian line in both hands and hammer toes. Cytogenetic analysis was performed with GTG-banding, C-banding and FISH analysis containing X centromeric probe, Yq12-qter locus specific probe and whole chromosome Y probe. An unbalanced Y/1 translocation was diagnosed: 45,X,der(1)inv(1)(p13;qter)t(Y;1)(pter-->q11;p13),-Y.     

Disruption of DMD and deletion of ACSL4 causing developmental delay, hypotonia, and multiple congenital anomalies

We have studied a male patient with significant developmental delay, growth failure, hypotonia, girdle weakness, microcephaly, and multiple congenital anomalies including atrial (ASD) and ventricular (VSD) septal defects. Detailed cytogenetic and molecular analyses revealed three de novo X chromosome aberrations and a karyotype 46,Y,der(X)inv(X) (p11.4q11.2)inv(X)(q11.2q21.32 approximately q22.2)del(X)(q22.3q22.3) was determined. The three X chromosome aberrations in the patient include: a pericentric inversion (inv 1) that disrupted the Duchenne muscular dystrophy (DMD) gene, dystrophin, at Xp11.4; an Xq11.2q21.32 approximately q22.2 paracentric inversion (inv 2) putatively affecting no genes; and an interstitial deletion at Xq22.3 that results in functional nullisomy of several known genes, including a gene previously associated with X-linked nonsyndromic mental retardation, acyl-CoA synthetase long chain family member 4 (ACSL4). These findings suggest that the disruption of DMD and the absence of ACSL4 in the patient are responsible for neuromuscular disease and cognitive impairment.     

Isolation and molecular analysis of inv dup(15) and construction of a physical map of a common breakpoint in order to elucidate their mechanism of formation

An inverted duplication of chromosome 15 [inv dup(15)] is the most common supernumerary marker chromosome, comprising approximately 50% of all chromosomes in this class. Structurally, the inv dup(15) is a mirror image with the central axis defining a distal break within either the heterochromatic alpha-satellite array or along the euchromatin in the long (q) arm of the chromosome. There are several types of inv dup(15), classified by the amount of euchromatic material present. Generally, they are bisatellited, pseudodicentric and have a breakpoint in 15q11-q14. A suggested mechanism of formation of inv dup(15) involves illegitimate recombination between homologous chromosomes followed by nondisjunction and centromere inactivation. The proximal portion of chromosome 15 contains several low-copy repeat sequence families and it has been hypothesized that errors in pairing among these repeats may result in structural rearrangements of this chromosome including the inv dup(15). To test this hypothesis and to determine the mechanism of formation, the inv dup(15) from four cases was isolated in somatic cell hybrids and polymerase chain reaction microsatellite markers were used to determine the origin of exchange. Two appeared to result from interchromosomal and two from intrachromosomal exchange, one of which occurred post-recombination. In addition, a detailed physical map of the breakpoint region in the largest inv dup(15) was constructed placing eight new sequence-tagged sites and ten new bacterial artificial chromosome markers in the region.     

Familial pericentric inversion of chromosome 1 with a note on reproductive risks

Summary An inversion of chromosome 1 was found in three normal members of a two generation family. G- and C-banding studies revealed inv(1)(p13q23). The problems encountered in counseling such normal carriers are discussed.     

Preferential maternal derivation in inv dup(15)

Summary Eight patients are reported with a de nov extra inverted duplicated chromosome 15. The abnormal chromosome was considered to be the same in all cases, but its precise delineation remained uncertain and was defined as either 15qter15q12::15q1215pter or 15pter15q11::15q1315pter. Analysis with various techniques of the satellite regions of the bisatellited chromosomes demonstrated maternal derivation in six and paternal derivation in one of the seven families. A nonsister chromatid exchange between the two homologous chromosomes 15 is considered a likely origin of the inv dup(15) in the cases with maternal derivation; in the only case of paternal derivation, however, the abnormal chromosome originated from one single chromosome 15. The clinical findings confirm that patients with inv dup(15) have mental and developmental retardation and are frequently affected by seizures, while severe physical malformations are absent.