A new chromosome 9 variant: an extra band within the 9qh region

The frequency of chromosomal abnormalities in patients with reproductive failure

OBJECTIVE

To investigate the ratio of chromosomal abnormalities in recurrent fetal wastage.

STUDY DESIGN

We conducted a study of the cytogenetic data of 645 couples (1290 patients) with recurrent fetal wastage examined at the Department of Medical Biology and Genetics, Trabzon, Turkey. Couples who had first trimester miscarriages/abortion, preceded or followed by a second or third trimester fetal death/fetal abnormalities were recruited from Obstetrics and Gynecology Clinics for cytogenetics analysis.

RESULTS

Chromosome abnormalities were found in 25 (3.86%) patients. The chromosomal abnormalities were structural (3.71%) and numerical (0.15%). Polymorphisms of heterochromatin blocks and inv(9) were shown in 115 (17.51%) patients.

CONCLUSIONS

Chromosome analyses are an important and necessary part of the etiological research in couples with recurrent fetal wastage.

An unusual familial chromosome 9 "variant" with variable phenotype: characterization by CGH analysis

Heterochromatin confined to pericentromeric and secondary constriction regions plays a major role in morphological variation of chromosome 9, because of its size and affinity for pericentric inversion. We report on a 6-year-old boy with growth and language delay, minor facial anomalies and unusual chromosome 9 variant with an extra-band in the centromeric region on the conventional karyotype. Subsequent analysis by FISH and CGH identified this variant as a dicentric chromosome 9 with a duplication of the 9p12-q21 region. An identical chromosome 9 variant was found in the mild language retarded brother and in the phenotypically normal father and grandfather. The presumed mechanism accounting for the phenotypic discordance observed in this family and the usefulness of CGH in characterization of such variants are discussed. To our knowledge, this is the first investigation of an unusual chromosome 9 variant by CGH.

Variants of chromosome 9 with additional euchromatic bands: two case reports

This paper documents a prenatal case of maternally inherited subtle duplication of chromosome 9 bands q21.1 to q21.2 and a second case with two G-bands within the 9qh region. Cytogenetic studies of these cases included G-banding, C-banding, fluorescent in situ hybridization (FISH) using chromosome 9 specific library probe, and the classical satellite probe. In both patients, the additional bands were G-bands and C-band negative. By FISH studies they were negative for the satellite heterochromatin probe and positive for the chromosome 9 painting probe. Therefore, the extra bands were presumably euchromatin and part of chromosome 9. The chromosome 9 variants and their possible mechanisms of origin are discussed.

Molecular cytogenetic studies of duplication 9q32-->q34.3 inserted into 9q13

Fluorescence in situ hybridization (FISH) studies using whole chromosome 9 painting probe, classical satellite (9q12-specific) probe and abl cosmid probe (locus: 9q34) were performed on a female infant who was born with multiple congenital anomalies and the karyotype 46,XX, 9q+. The results of FISH confirm the euchromatic nature of the extra material on the long arm of chromosome 9, and provide evidence that it is of chromosome 9 origin. The structural rearrangement has probably resulted from an insertion of a duplicated segment 9q32-->q34.3 into band q13, as shown by the abl cosmid probe. The clinical features in this patient are similar to the previously reported cases of partial trisomy 9q3.

Constitutional heteromorphism of 9q13 --> q21 in a patient with chronic myelogenous leukemia

Cytogenetic studies were carried out in a 44-year-old white male because of newly diagnosed chronic myelogenous leukemia. His initial bone marrow study revealed 46,XY, var(9)(q13 -->q21)/46,XY,var(9) (q13-->q21), t(9;22)(q34;q11) karyotypes and later he also acquired a 47,XY,+8,var(9)(q13-->q21), t(9;22)(q34;q11) clone. The var(9)(q13-->q21) heteromorphism was observed in the normal 9 homolog, in 200 GTG-banded bone marrow metaphases in seven cytogenetic studies (1988-90). This heteromorphism was observed in the normal cell line, in the two chronic myelogenous leukemia-related clones, as well as in 100 mitogen-induced peripheral blood lymphocytes, indicating its constitutional nature. This seems to be the first report of var(9)(q13 --> q21) heteromorphism, involving GTG-positive euchromatic band, in a chronic myelogenous leukemia proband.

An extra band within the human 9qh+ region that behaves like the surrounding constitutive heterochromatin

An extra variant G band in a human 9qh+ region was analysed in normally condensed and 5-azacytidine undercondensed chromosomes. Fluorescence in situ hybridisation showed that specific, classical, alphoid and beta satellite DNA was not present. Nevertheless, this extra band behaves like the surrounding heterochromatin because (1) its chromatin fibres showed condensation inhibition after 5-azacytidine treatment, as confirmed by electron microscopy, and (2) it was not affected by in situ digestion with the restriction endonucleases AluI and Sau3A. These results suggest that this variant band may correspond to euchromatin that has become inactivated by a position effect.

Evidence of chromosome 9 origin of the euchromatic variant band within 9qh

Fluorescence in-situ hybridization studies using a whole chromosome 9 painting probe were performed on three individuals from two different families, who carry a chromosome 9 variant with an extra band within the elongated 9qh region. The results confirm the euchromatic nature of the extra band, and provide evidence that it is of chromosome 9 origin. This variant band, which may not be very rare, thus possibly results from a duplication of a segment of 9qh plus band p12 or part of band q21.