An attempt to define 1qh+, 9qh+, and 16qh+

Summary The lengths of the secondary constrictions of chromosomes 1, 9, and 16 vary with the degree of contraction of the chromosomes but these constrictions contract to a lesser degree than the euchromatic portions of the chromosomes. The regression coefficient for the regression of the length of the secondary constriction on the length of the euchromatic part of the chromosomes is shown to be larger for large constrictions. It is furthermore shown that there is a linear correlation between the regression coefficient and the size of the secondary constriction in question. This linear correlation makes it possible to correct the lengths of the secondary constrictions to the lengths expected when contraction is average. The correction method is used in a sample of 30 couples, and on the basis of this sample, the normal limits for the lengths of the secondary constrictions in chromosomes 1, 9, and 16 are defined.     

Subfertile couple with t(4;22)(q23;q11.2)

A couple was referred for cytogenetic examination due to idiopathic miscarriages. The proband proved to be a carrier of chromosomal translocation and her partner's karyotype was found to be normal. The karyotype of the proband is 46,XX,t(4;22)(q23;q11.2) and can be regarded as a reason of fertility problems in the investigated couple. The risk of further miscarriages is high, but the risk of a progeny with abnormal karyotype is rather low, as the progeny would probably have lethal imbalances.     

An extra band in human 9qh+ chromosomes

Summary Chromosome analysis of G-banded cells from nine individuals showed that 9qh+ chromosomes have an extra band in the h region in approx. 3 to 50% of the cells.     

The inv(16) cooperates with ARF haploinsufficiency to induce acute myeloid leukemia

The inv(16) is one of the most frequent chromosomal translocations associated with acute myeloid leukemia (AML) and creates a chimeric fusion protein consisting of most of the runt-related X1 co-factor, core binding factor beta fused to the smooth muscle myosin heavy chain MYH11. Expression of the ARF tumor suppressor is regulated by runt-related X1, suggesting that the inv(16) fusion protein (IFP) may repress ARF expression. We established a murine bone marrow transplant model of the inv(16) in which wild type, Arf+/-, and Arf-/- bone marrow were engineered to express the IFP. IFP expression was sufficient to induce a myelomonocytic AML even when expressed in wild type bone marrow, yet removal of only a single allele of Arf greatly accelerated the disease, indicating that Arf is haploinsufficient for the induction of AML in the presence of the inv(16).     

Classification of qh regions in human chromosomes 1, 9, and 16 by C-banding

Summary We present a classification for secondary constriction (qh) regions with C-banding technique in chromosomes 1,9, and 16 by means of comparing them to the short arm of chromosome 16. It is simple and convenient and can be used routinely. It can be incorporated into the modified Paris nomenclature system.     

Trisomy 9 associated with an enlarged 9qh segment in a liveborn

Summary This report describes the third case of a complete trisomy 9 in a liveborn infant. A tentative explanation for the origin of a very large h-segment which was not present in either parent of the proposita is put forward.     

Familial inv(2) (p2300q11.2)

A hitherto undescribed inv(2) (p2300q11.2) was found in 2 generations of a family ascertained through a holoprosencephalic liveborn boy with normal karyotype. This inversion, quite probably not related to the child malformations, does not seem neither impair reproductive fitness nor to yield viable recombination aneusomies.     

A possible clinical implication of homozygous inversions of 9qh regions with Cornelia de Lange syndrome (CLS)

Several investigators have attempted to correlate chromosomal abnormalities with Cornelia de Lange Syndrome (CLS), but none of them have been conclusive. The homozygous inversion of 9qh found in the present case has not been found previously. It remains to be clarified whether the presence of this finding in CLS was simply a coincidence or whether homozygosity for such inversions may result in CLS.     

Prenatal diagnosis of a 46,XX,inv(12)pat/47,XX,i(Xq),inv(12)pat

Summary A 46,XX,inv(12)pat/47,XX,i(Xq),inv(12)pat was diagnosed prenatally in a 36-year-old woman whose husband was a known carrier of a pericentric inversion of chromosome 12. The diagnosis was confirmed in fetal tissue. Terminal bromodeoxyuridine (BrdU) labelling demonstrated that in the line with 46 chromosomes one X was late replicating, while one X and the i(Xq) were late replicating in 100% of the cells with 47 chromosomes. We present the first case of this type of sex chromosome mosaicism. Genetic counseling presented difficulties since it was not possible to predict the fetal phenotype.     

inv(9)(p24q13) in three sterile brothers

Only nine non-polymorphic constitutional pericentric inversions of chromosome 9 have been described. We report on a familial inv(9)(p24q13) associated with sterility in three brothers. The mother's chromosomes were normal in blood lymphocytes (n=130); the father was already deceased and his karyotype unknown. However, the presence of any of the maternal chromosomes 9 (as assessed by C-banding) in her carrier children is inconsistent with the assumption of maternal mosaicism. Two single sisters were also carriers. The same rearranged chromosome 9 in the three sterile brothers can hardly be regarded as a fortuitous association, especially when the breakpoints are almost identical to those of the sole inversion previously found in an azoospermic male. If their father was a carrier, the observed sterility may be the result of 'chromosome anticipation', a phenomenon already invoked for certain familial chromosomal rearrangements.     

Mitotic disturbances associated with inversion 9qh. A case report

A 25-year-old female with history of spontaneous abortion and subsequent birth of Down syndrome child was referred for chromosome analysis. Her karyotype revealed 46, XX with pericentric inversion of 9 qh, while her husband was normal with 46, XY chromosomes. Metaphase analysis of the female showed 20.5% cells with premature centromere division, 4% with endoreduplication, 2% with polyploidy and 9.33% aneuploidy. These frequencies were considerably higher as compared to a normal control. These observations suggest that inv (9qh) might have some interchromosomal effect leading to higher incidence of mitotic disturbances, finally resulting in aneuploidy. This predisposition is evident by spontaneous abortion and later birth of a Down syndrome child.     

Trisomy 13qter by tandem duplication 46, XX, dir dup 13 (q21 qter), 9qh+]

A tandem translocation of chromosome 13-46,XXdup13(q21 leads to qter)--occurred de novo in a patient with the following features: normal birthweight; early feeding difficulties; mild psychomotor retardation; low set hairline on the forehead; thick eyebrows; long, upturned eyelashes; pointed nose; micrognathia; large, flat, posteriorly rotated ears; multiple hemangiomata; normal hematological status. The hypothesis of an unequal crossing-over is discussed, as well as the possibility of constructing a phenotypic map of chromosome 13.     

Molecular topography of the secondary constriction region (qh) of human chromosome 9 with an unusual euchromatic band.

Heterochromatin confined to pericentromeric (c) and secondary constriction (qh) regions plays a major role in morphological variation of chromosome 9, because of its size and affinity for pericentric inversion. Consequently, pairing at pachytene may lead to some disturbances between homologous chromosomes having such extreme variations and may result in abnormalities involving bands adjacent to the qh region. We encountered such a case, where a G-positive band has originated de novo, suggesting a maternal origin from the chromosome 9 that has had a complete pericentric inversion. In previously reported cases, the presence of an extra G-positive band within the 9qh region has been familial, and in the majority of those cases it was not associated with any clinical consequences. Therefore, this anomaly has been referred to as a "rare" variant. The qh region consists of a mixture of various tandemly repeated DNA sequences, and routine banding techniques have failed to characterize the origin of this extra genetic material. By the chromosome in situ suppression hybridization technique using whole chromosome paint, the probe annealed with the extra G-band, suggesting a euchromatic origin from chromosome 9, presumably band p12. By the fluorescence in situ hybridization technique using alpha- and beta-satellite probes, the dicentric nature was further revealed, supporting the concept of unequal crossing-over during maternal meiosis I, which could account for a duplication of the h region. The G-positive band most likely became genetically inert when it was sandwiched between two blocks of heterochromatin, resulting in a phenotypically normal child. Therefore, an earlier hypothesis, suggesting its origin from heterochromatin through so-called euchromatinization, is refuted here.(ABSTRACT TRUNCATED AT 250 WORDS)     

Impact of pericentric inversion of Chromosome 9 [inv (9) (p11q12)] on infertility

BACKGROUND:

One of the frequent occurrences in chromosome rearrangements is pericentric inversion of the Chromosome 9; inv (9) (p11q12), which is consider to be the variant of normal karyotype. Although it seems not to correlate with abnormal phenotypes, there have been many controversial reports indicating that it may lead to abnormal clinical conditions such as infertility. The incidence is found to be about 1.98% in the general population.

MATERIALS AND METHODS:

We investigated the karyotypes of 300 infertile couples (600 individuals) being referred to our infertility clinic using standard GTG banding for karyotype preparation.

RESULTS:

The chromosomal analysis revealed a total of 15 (2.5%) inversions, among these, 14 male patients were inversion 9 carriers (4.69%) while one female patient was affected (0.33%). The incidence of inversion 9 in male patients is significantly higher than that of normal population and even than that of female patients (P< 0.05).

CONCLUSIONS:

This result suggests that inversion 9 may often cause infertility in men due to spermatogenic disturbances, which are arisen by the loops or acentric fragments formed in meiosis.