Molecular analysis of a case of meiotic recombination leading to cri-du-chat syndrome

This paper describes a molecular investigation of a woman with an apparent large pericentric inversion of chromosome 5, inv(5)(p14;q35), and one normal chromosome 5 and her child, who was born with cri-du-chat syndrome. The four chromosome 5 homologs from the proband and his mother were isolated in somatic cell hybrids, and their haplotypes were determined at nine loci polymorphic for restriction enzyme sites. The deleted chromosome in the proband was shown to carry alleles from both maternal homologs, verifying molecularly that a meiotic recombination event in the mother gave rise to her son's deleted chromosome 5. The single crossover was presumably near the centromere.     

"Cri-du-chat" syndrome in a patient born to a mother with a paracentric inversion of chromosome 5q

We report the case of a female child presented at birth with hypotonia, growth retardation and respiratory distress. Chromosome study from peripheral blood showed a 46,XX,del(5)(p14pter) karyotype. Parental chromosome studies revealed that the mother carried an apparently balanced paracentric inversion of long arms of one chromosome 5, giving the karyotype 46,XX,inv(5)(q12q32), whereas paternal karyotype was normal. The maternal abnormality was confirmed by fluorescence in situ hybridization (FISH) and was not present in the daughter's metaphases. Microsatellite analysis in the proposita and her parents permitted us to conclude that the deleted chromosome 5 was paternal in origin, as usually described. Therefore, as might have been expected, maternal paracentric inversion of chromosome 5q and "cri-du-chat syndrome" presented by the daughter were not related.     

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.     

A fetus with recombinant of chromosome 8 inherited from her carrier father

Summary A pericentric inversion of chromosome 8, inv(8)(p23q22), in a male carrier resulted in an unbalanced recombinant, rec(8)dup q, inv(8)(p23q22), which was diagnosed prenatally. The features seen in the aborted fetus resembled the features seen in a previously affected child who received the identical recombinant from her carrier mother. In this particular inversion involving chromosome 8, both male and female carriers risk producing an unbalanced progeny. Different familial pericentric inversions are reviewed for the presence or absence of unbalanced recombinants.     

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.     

Cri-du-chat syndrome and two other deformed children in a family carrying a pericentric inversion or insertion of chromosome 5

Chromosomal syndromes may result from extremely small cytogenetic alterations, involving as little as one chromosomal sub-band. An example is the cri-du-chat (cat cry) syndrome, in which the critical deletion appears to involve the sub-bands 5p15.1-3. Aside from a sporadic deletion of 5p, the loss of material may result from an interstitial deletion, caused by the malsegregation of a balanced parental translocation, or, in exceptional cases, as the consequence of a sporadic or familial chromosomal inversion which has been modified by unequal crossing-over (recombination aneuploidy). In addition, in certain children with the clinical syndrome (11 of 331 in a recent review) the deletion cannot be proven cytogenetically and is presumed to be submicroscopic. In the case described here, an intrachromosomal rearrangement of chromosome 5--an invper(5)(p15q14 or 15) or an ins(5) (p15q12q12)--is segregating in the maternal family. Three of the four children born to the couple were abnormal. The first boy, affected with cleft lip, pyloric stenosis and inguinal hernias, died at 4 months of age. The second died at 3 weeks with microcephaly and agenesis of the corpus callosum, cleft palate, heart malformation, and sexual ambiguity. A third boy, now 14 years old, is phenotypically normal and has a normal karyotype. The female proband, seen by us at 9 years of age, showed the clinical features of the cri-du-chat syndrome, with severe psychomotor and staturoponderal retardation, facial dysmorphism, congenital heart defect, and the peculiar voice for which she had received the nickname of "kitten". Her karyotype shows the same variation of chromosome 5 present in her mother and grandmother, characterized on G bands by an additional dark band on 5p15. As there is no evidence for a reciprocal translocation in the mother, the most probable explanation is that of a familial inversion or insertion within chromosome 5. This rearrangement, subject to meiotic modifications, could have been responsible for the complex malformations observed in 3 of the 4 children, including our proband who has a clinical diagnosis of the cri-du-chat syndrome.     

Cloning, sequencing, and analysis of inv8 chromosome breakpoints associated with recombinant 8 syndrome

Rec8 syndrome (also known as "recombinant 8 syndrome" and "San Luis Valley syndrome") is a chromosomal disorder found in individuals of Hispanic descent with ancestry from the San Luis Valley of southern Colorado and northern New Mexico. Affected individuals typically have mental retardation, congenital heart defects, seizures, a characteristic facial appearance, and other manifestations. The recombinant chromosome is rec(8)dup(8q)inv(8)(p23.1q22.1), and is derived from a parental pericentric inversion, inv(8)(p23.1q22.1). Here we report on the cloning, sequencing, and characterization of the 8p23.1 and 8q22 breakpoints from the inversion 8 chromosome associated with Rec8 syndrome. Analysis of the breakpoint regions indicates that they are highly repetitive. Of 6 kb surrounding the 8p23.1 breakpoint, 75% consists of repetitive gene family members-including Alu, LINE, and LTR elements-and the inversion took place in a small single-copy region flanked by repetitive elements. Analysis of 3.7 kb surrounding the 8q22 breakpoint region reveals that it is 99% repetitive and contains multiple LTR elements, and that the 8q inversion site is within one of the LTR elements.     

Meiotic analysis of a pericentric inversion, inv(7) (p22q32), in the father of a child with a duplication-deletion of chromosome 7

In a family in which a large pericentric inversion of chromosome 7 is segregating, two of the four progeny of inversion heterozygotes show severe psychomotor retardation and have the karyotype 46,XX,rec(7),dup q,inv(7)(p22q32), derived from crossing-over within the inversion. Meiotic analysis in one of the heterozygotes revealed no evidence of inversion loops in well-spread pachytene cells. In approximately 20% of cells in diakinesis, the presumptive bivalent 7 had only one chiasma. Two alternatives to the reversed loop mode of meiotic pairing of inversions are proposed. Review of the literature supports the view that "small" pericentric inversions have a much better genetic prognosis than "large" pericentric inversions.     

Recombination aneusomy of subtelomeric regions of chromosome 5, resulting from a large familial pericentric inversion inv(5)(p15.33q35.3)

We present a family with three cases of recombination aneusomy rec(5)dup(5q) originating from a large parental pericentric inversion of chromosome 5. The proband--a 6-year-old girl with mental retardation, speech delay, microcephaly, and slight facial dysmorphism--was referred for subtelomere testing. FISH with a Multiprobe Chromoprobe T System (CytoCell) and with several BAC clones mapping to both subtelomere regions of chromosome 5, revealed a recombinant chromosome rec(5)dup(5q) originating from a paternal pericentric inversion inv(5)(p15.33q35.3). The same inversion was present in the proband's father's twin-brother and rec(5)dup(5q) was also identified in his two mentally retarded daughters. The distance of breakpoints from the telomere was: 0.234-1.4 Mb for 5p and 4.1-4.8 Mb for 5q. HR-CGH analysis confirmed the duplication of the 5q subtelomeric region but did not identify any concomitant deletion in the 5p subtelomere. Precise mapping of the aneusomic regions in the proband enabled mapping the cat cry and speech delay to 5p15.33, making the earlier localizations of these features more precise. Our family shows that the large pericentric inversion with both breakpoints at subtelomeric regions of chromosome 5 is associated with a high risk of rec(5)dup(5q) in the progeny.     

Recombinant chromosome 14 due to maternal pericentric inversion

Chromosome 14 is often involved in various chromosome rearrangements, most of them balanced. Human chromosome 14 is acrocentric, so its pericentric inversions are extremely rare (only few cases have been described in the literature). Here we report on a boy with congenital malformations and recombinant chromosome 14 inherited from his mother carrying a pericentric inversion. The proband's G-banded chromosome analysis revealed derivative chromosome 14. Comparative genomic hybridization analysis identified duplication of the terminal part of chromosome 14q ish cgh dup(14)(q32.1qter). This abnormality has been confirmed by custom BAC FISH analysis. His mother's karyotype was 46,XX,inv(14)(p11.2q32.1).     

A large pericentric inversion of human chromosome 8.

A large pericentric inversion, inv(8) (p11q24), was ascertained in a male investigated because his wife had had repeated miscarriages. The inversion segregated in 3 generations of the family, and no chromosomally unbalanced offspring were detected. The miscarriage and the inversion could not be causally related.     

Gene assignment of Zellweger syndrome to 7q11.23: report of the second case associated with a pericentric inversion of chromosome 7

Summary The case of a newborn girl with Zellweger syndrome and a pericentric inversion of chromosome 7, 46,XX, inv(7)(p12q11.23), is reported. The diagnosis was confirmed by marked deficiency of peroxisomal beta-oxidation enzymes in hepatic cells from autopsy samples. This is the second case of Zellweger syndrome associated with a rearrangement of chromosome 7, the tentative gene assignment to 7q11 being further supported; the gene is probably confiend to 7q11.23.     

Breakpoint cloning and haplotype analysis indicate a single origin of the common Inv(10)(p11.2q21.2) mutation among northern Europeans

The pericentric inv(10)(p11.2q21.2) mutation has been frequently identified in cytogenetic laboratories, is phenotypically silent, and is considered to be a polymorphic variant. Cloning and sequencing of the junction fragments on 10p11 and 10q21 revealed that neither inversion breakpoint directly involved any genes or repetitive sequences, although both breakpoint regions contain a number of repeats. All 20 apparently unrelated inv(10) families in our study had identical breakpoints, and detailed haplotype analysis showed that the inversions were identical by descent. Thus, although considered a common variant, inv(10)(p11.2q21.2) has a single ancestral founder among northern Europeans.     

A new case of partial 14q31.3-qter trisomy due to maternal pericentric inversion

Chromosome 14 is often involved in chromosome rearrangements, although pericentric inversions are rare. Here we report a mother carrying a pericentric inversion of chromosome 14, and her daughter with recombinant chromosome characterized by a partial distal 14q trisomy. Principal clinical findings of the child include facial anomalies, microcephaly, developmental delay, hypotonia and cardiac malformation. Her final karyotype was 46,XX,rec(14)dup(14q)inv(14)(p12q31)mat[20], arr 14q31.3qter(85,427,839–106,356,482)x3. This report brings new data about clinical features of partial 14q trisomy and molecular analysis enables the visualization of genes involved in the segment duplicated.     

Chromosomal abnormalities in hypoprolific boars

Four new chromosomal rearrangements are reported in the domestic pig: 3 reciprocal translocations, rcp(4;12)(p13;q13) in a crossbred boar, rcp(1;7)(q17;q26) in a Large White purebred boar, rcp(1;6)(q17;q35) in a purebred synthetic paternal line boar, and a pericentric inversion inv(2)(p13q11) in a crossbred boar. The 1/7 reciprocal translocation and the pericentric inversion were detected in animals that had sired small litters. The effect of the 1/7 translocation was accurately determined: -4.5 piglets born per litter, i.e. -36%. Both the 1/6 and 1/7 reciprocal translocations were of maternal origin. All the chromosomal rearrangements were highlighted using GTG and/or RBG banding techniques. Chromosome painting experiments were also carried out to confirm the proposed hypotheses for the three reciprocal translocations.     

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     

Investigation of the origins of human autosomal inversions

A significant proportion of both pericentric and paracentric inversions have recurrent breakpoints and so could either have arisen through multiple independent events or be identical by descent (IBD) with a single common ancestor. Of two common variant inversions previously studied, the inv(2)(p11q13) was genuinely recurrent while the inv(10)(p11.2q21.2) was IBD in all cases tested. Excluding these two variants we have ascertained 257 autosomal inversion probands at the Wessex Regional Genetics Laboratory. There were 104 apparently recurrent inversions, representing 35 different breakpoint combinations and we speculated that at least some of these had arisen on more than one occasion. However, haplotype analysis identified no recurrent cases among eight inversions tested, including the variant inv(5)(p13q13). The cases not IBD were shown to have different breakpoints at the molecular cytogenetic level. No crossing over was detected within any of the inversions and the founder haplotypes extended for variable distances beyond the inversion breakpoints. Defining breakpoint intervals by FISH mapping identified no obvious predisposing elements in the DNA sequence. In summary the vast majority of human inversions arise as unique events. Even apparently recurrent inversions, with the exception of the inv(2)(p12q13), are likely to be either derived from a common ancestor or to have subtly different breakpoints. Presumably the lack of selection against most inversions allows them to accumulate and disperse amongst different populations over time. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Pericentric inversions of the X chromosome. A new observation and review of the published cases

A pericentric inversion of the X chromosome-inv(X) (p11.3q22) is transmitted in 3 generations. Male and female carriers are normal. The proposita is tetraplegic, severely retarded and suffers from general seizures. Grand mal seizures are known in the mother and grandmother. Different proportions of inactive X chromosomes in the proposita and the normal sister are discussed. The published cases of inv(X) are reviewed.     

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.     

Pericentric inversion inv(7)(p11q21.1): report on two cases and genotype-phenotype correlations

We report on two unrelated cases of pericentric inversion 46,XY,inv(7)(p11q21.1) associated with distinct pattern of malformation including mental retardation, development delay, ectrodactyly, facial dismorphism, high arched palate. Additionally, one case was found to be characterized by mesodermal dysplasia. Cytogenetic analysis of the families indicated that one case was a paternally inherited inversion whereas another case was a maternally inherited one. Molecular cytogenetic studies have shown paternal inversion to have a breakpoint within centromeric heterochromatin being the cause of alphoid DNA loss. Maternal inversion was also associated with a breakpoint within centromeric heterochromatin as well as inverted euchromatic chromosome region flanked by two disrupted alphoid DNA blocks. Basing on molecular cytogenetic data we hypothesize the differences of clinical manifestations to be produced by a position effect due to localization of breakpoints within variable centromeric heterochromatin and, alternatively, due to differences in the location breakpoints, disrupteding different genes within region 7q21-q22. Our results reconfirm previous linkage analyses suggested 7q21-q22 as a locus of ectrodactily and propose inv (7)(p11q21.1) as a cause of recognizable pattern of malformations or a new chromosomal syndrome.