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R A Conte

Publications and source records attributed to R A Conte.

At least 37 records · Page 2Linked to original sources
PubMed1997

Characterization of two extreme variants involving the short arm of chromosome 22: are they identical?

The heteromorphic nature of the short-arms of human acrocentric chromosomes is considered the norm without any dire consequences. We characterized two highly unusual chromosome 22 variants with extremely enlarged short arms by routine and molecular cytogenetic techniques. Routine banding revealed that the two variants were not alike. Therefore, a characterization by fluorescent in situ hybridization (FISH) technique became warranted and revealed their remarkable differences. The first variant apparently had a tandem duplication of bands p11.2-->p13, while the second variant had a loss of the beta-satellite and ribosomal DNA regions with an apparent amplification of the satellite III region. The formation of these extremely enlarged regions can occur by a variety of mechanisms whose clinical significance remains obscure.

Adult↗
PubMed1997

Tandem duplication of chromosome 14 (q12q13).

A nine-years-old Egyptian boy was referred for speech and language delay. He has an I.Q. of 35 which is in the moderately to severely delayed range. Routine cytogenetic and FISH-techniques revealed a de novo tandem duplication of chromosome 14 bands q12 and q13, i.e., 46, XY, dup (14)(q12q13) and there are no investigations reporting a direct de novo duplication for this region.

Child↗
PubMed1997

An unusual G-negative band within 1qh region a rare variant or an abnormality?

Morphological variations due to heterochromatic DNA of the secondary constriction region (qh) of human chromosome 1 are considered normal. The structural abnormalities involving or in association within the qh region have been difficult to characterize by routine cytogenetic methods and in turn have often gone undetected. In the past, the presence of a G-negative band within the qh region of chromosome 9 has been considered as a rare or unusual variant. Fortuitously, we were referred two cases where a G-negative band was embedded within the secondary constriction region of chromosome 1. Whole chromosome #1 specific painting probe, did hybridize to the band. Both patients have speech delay. Unfortunately, the parents were not available to confirm the mode of inheritance, nor could a definite conclusion be reached concerning its morbidity. Nevertheless, we are tempted to hypothesize that this is an unusual variant where a G-negative band apparently became genetically inert when it was sandwiched between two blocks of heterochromatin. Similar to a rare variant of chromosome 9 it could be found in the qh region of chromosome 16 as well, whose clinical consequences remain obscure.

Child, Preschool↗
PubMed1996

A unique genomic sequence in the Wolf-Hirschhorn syndrome [WHS] region of humans is conserved in the great apes.

The Wolf-Hirschhorn syndrome (WHS) is caused by a partial deletion in the short arm of chromosome 4 band 16.3 (4p 16.3). A unique-sequence human DNA probe (39 kb) localized within this region has been used to search for sequence homology in the apes' equivalent chromosome 3 by FISH-technique. The WHS loci are conserved in higher primates at the expected position. Nevertheless, a control probe, which detects alphoid sequences of the pericentromeric region of humans, is diverged in chimpanzee, gorilla, and orangutan. The conservation of WHS loci and divergence of DNA alphoid sequences have further added to the controversy concerning human descent.

Abnormalities, Multiple↗
PubMed1996

Molecular characterization of an unusual variant of the short arm of chromosome 15 by FISH-technique.

One of the most frequent translocations involving the long arm of chromosome Y with autosomes is with the short arm of chromosome 15. The regions which are involved in this translocation fluoresce brightly, are highly heteromorphic and thus escape detection. Therefore, these abnormalities could not be fully characterized, especially in cases where parents are not available or paternity is disputed. Results from the employment of the selective staining techniques DA/DAPI and Q-banding have been inconclusive. FISH-technique using whole chromosome painting (WCP) probes should be used to decipher such translocations. We present a case where, even after using a battery of probes, the origin of extra material on chromosome 15p could not be identified though it was not a part of Yq.

Chromosomes, Human, Pair 15↗
PubMed1996

Mapping the homolog of the human Rb1 gene to chromosome 14 of higher primates.

The Rb1 gene has been implicated with retinoblastoma and is located on human Chromosome (Chr) 13q14.2. A unique sequence human Rb1 cosmid DNA probe has been used to localize this region on apes' Chr 14 by the FISH technique. The conservation of the Rb1 gene in higher primates at the corresponding equivalent chromosome locus (14q14) of the human may serve as a phylogenetic marker to further trace the evolutionary pathway of human descent.

Animals↗
PubMed1996

Molecular cytogenetic characterization of breakpoints involving pericentric inversions of human chromosome 9.

Pericentric inversions involving the secondary constriction (qh) region of chromosome 9 are considered to be normal variants. The evolutionary mechanisms and conservation of these inversions via Mendelian fashion have been investigated since the advent of banding techniques. Routine cytogenetic techniques cannot provide the fine characterization necessary to determine the type of genetic material involved in these rearrangements. Therefore, the fluorescence in situ hybridization technique with the human centromere-specific alpha satellite and the beta satellite (D9Z5) and classical satellite (D9Z1) human DNA probes were used to identify the breakpoints of chromosome 9 pericentric inversions. Four unique types of pericentric inversions involving the 9qh region were observed, and the mechanism may be due to breakage and reunion at the proposed breakpoints. They are: type A inversions consist of breakpoints within the alpha and beta satellite DNA regions; type B consist of breakpoints within the beta satellite DNA region and band 9q13; type C involve breakage within the beta and classical satellite DNA regions, and type D have breakpoints within the alpha and classical satellite DNA regions. Obviously, reshuffling of satellite DNA sequences has occurred, which has given rise to a variety of heteromorphisms whose clinical significance remains obscure.

Chromosome Breakage↗
PubMed1996

Molecular characterization of 21p- variant chromosome.

Fortuitously, within a 1-month period, we were referred two individuals for routine cytogenetic amniocenteses involving one chromosome 21 from each patient, which had apparently lost the entire short arm and a major portion of the centromeric alphoid sequences in their amniocytes. Breakage may have occurred within alphoid sequences resulting in extreme variants. Variations of a similar nature were originally referred to as Christchurch (Ch1) chromosomes and have been wrongly determined to be abnormal. The 21p- chromosome variants were similar in both cases, though they are from unrelated individuals. These rare variants, whose origins were both maternal and have no clinical consequences, were characterized by the FISH-technique to provide a greater degree of certainty.

Amniocentesis↗
PubMed1996

Centromeric alphoid sequences are breakage prone resulting in pericentromeric inversion heteromorphism of qh region of chromosome 1.

Structural variations in the pericentromeric region of chromosome 1 are considered the norm. We characterized a chromosome 1 with an inversion by FISH-technique and suggested that the origin of pericentromeric heteromorphism is far more complex than previously suggested. It is postulated that similar to the centromeric alphoid DNA sequences of chromosome 9, chromosome 1 also possesses a "breakage prone" centromeric domain which may be a possible cause of such inversions involving the secondary constriction region.

Adult↗
PubMed1996

Characterization of a de novo t(Y;9) (q11.2;q22) by FISH technique.

A new case with a de novo translocation involving the long arms of chromosomes Y and 9 i.e. 46, X, t(Y;9) (q11.2;q22) was noted in a phenotypically normal male as revealed by GTG technique and subsequently confirmed using dual color whole chromosome painting probes. Since the Yq11.2 region was involved in the translocation the fecundity status of the individual has been questioned. Previous cases with (Y;autosomal) translocations have produced males with azoospermia, a variety of male gamete deformities and idiopathic sterility. The azoospermic factor (AZF) on the distal Yq11 band, which apparently controls spermatogenesis, may have been adversely affected due to a microdeletion, rearrangement or complete loss as a result of the translocation mechanism. Testicular histological and fertility tests of the proband at a postpubescent age will reveal the status. The sex determining region (SRY) on the Yp, which has been equated with the testis determining factor (TDF), is believed to be intact. Dual color whole chromosome painting probes, which served as an important adjunct to GTG banding, increased the degree of certainty for the characterization of the involved translocation. A concise review of balanced (Y ; autosome) translocation cases are annotated here.

Chromosomes, Human, Pair 9↗
PubMed1995

Clinical manifestations of trisomy 4p syndrome.

UNLABELLED: Trisomy 4p syndrome is a distinct clinical entity which was noted almost a quarter century ago by Wilson et al. [71] and later was delineated by Gonzalez and colleagues [29]. The variation in the length of duplicated segment usually associated with monosomy of other genetic material which has resulted in confusion and as a result a so-called 4p syndrome could not be recognized without cytogenetic analysis. We wish to draw the attention of clinicians to this subject by presenting the description of over 75 cases including one from our clinic and stress the point that molecular approaches are imperative to characterize this anomaly. After extensive review, it appears that patients retaining at least the distal two-thirds to the entire short arm share an overlapping phenotypic expression that constitutes pure trisomy 4p syndrome which includes prominent glabella, bulbous nose with flat or depressed nasal bridge, retrognathia, pointed chin, short neck with low hairline, enlarged ears with abnormal helix and antihelix, rocker-bottom feet with prominent heel. Arachnodactyly and camptodactyly. Molecular characterization of 4p is imperative. We have also included an extensive bibliography for clinicians who may find it useful as a single reference source for evaluating their future cases. CONCLUSION: The 4p-syndrome is a distinct entity but without cytogenetic evaluation, the syndrome can not be recognized.

Abnormalities, Multiple↗
PubMed1995

Molecular characterization of trisomic segment 3p24.1-->3pter: a case with review of the literature.

A 1-year-old male infant was found to have a de novo unbalanced translocation, resulting in trisomy for a portion of the short arm of chromosome 3, i.e. 46,XY,der(7)t(3;7) (p24.1;p22). Previous cases with a so-called "trisomy 3p syndrome" were evaluated by GTG banding, while we attempted to characterize the present case by the FISH-technique. The major clinical features included: dysmorphic ears, decreased muscle tone and seizure episodes associated with fever, which are concordant with "trisomy 3p syndrome". The most common malformations of trisomy 3p syndrome are: psychomotor and mental retardation, short neck, hypertelorism/telecanthus and congenital heart defects. Predominantly, the 3p trisomies have been maternally derived and the major mechanism of inheritance is due to a malsegregation of the chromosomes that are involved in a parental balanced translocation. A review of 44 cases from 35 studies revealed that the clinical manifestations have been quite varied, depending upon the amount of 3p2 material in the trisomic state, but interestingly a recognizable pattern of features was obvious in those cases whose cytogenetic findings and clinical histories were known.

Chromosomes, Human, Pair 3↗
PubMed1995

Characterization of a ring chromosome 21 by FISH-technique.

Ring chromosomes 21 that contain two copies of the Down syndrome critical region (DCR1), thereby contributing to trisomic dosage, have not been fully characterized by routine cytogenetic methods in the past. We therefore employed the fluorescence in situ hybridization (FISH) technique, using a battery of chromosome 21 probes and conclude that the ring resulted from a centromere to centromere and long arm to long arm fusion that contains alpha-satellite DNA and two copies of the D21S65 locus, but lacks beta-satellite DNA and telomeric DNA. Consequently, we suggest that the origin of the ring may be due to the misdivision of the centromere following the duplication of the long arm, forming a monocentric isochromosome followed by breakage in a region distal to the D21S65 locus and proximal to the telomeric sequences followed by reunion of the broken ends resulting in a monocentric ring. Different ring configurations or fragments were not detected, suggesting that the ring chromosome was highly stable. Apparently, the presence of two copies of Down syndrome loci within the ring chromosome, along with one copy on the normal homologue, caused the clinical consequences of Down syndrome.

Centromere↗
PubMed1995

Enumeration of semen leucocytes by fluorescence in situ hybridisation technique.

Aim-To determine whether the fluorescent in situ hybridisation technique (FISH) using a total human DNA genomic probe can be used to enumerate semen leucocytes.Methods-Semen samples from five donors were subjected to a mild KC1 solution. These samples were then biotin labelled under FISH conditions using a total human DNA genomic probe and the leucocyte counts were determined. To check the accuracy of the technique a monoclonal antibody against the common leucocyte antigen CD45 [KC56(T-200)] served as a control. An isotypic control for [KC56(T-200)], the immunoglobulin [MsIgG1], served as a secondary control.Results-Semen leucocytes stained by the FISH technique were easily detected because of their distinct bright yellow colour, while the sperm cells were red. The leucocyte count ranged from 0.5 to 4.9 x 10(6) per ml of semen. KC56(T-200) and its isotypic control MsIgG1, which served as control for the FISH technique, accurately identified 94% and 97% of the semen leucocytes of a control donor, respectively.Conclusions-The FISH technique using a total human DNA probe can accurately and effectively enumerate the overall leucocyte population in semen.

Journal Article↗
PubMed1995

Mechanisms of the origin of a G-positive band within the secondary constriction region of human chromosome 9.

We report on a so-called rare variant where a G-positive band was sandwiched within the secondary constriction (qh) region of chromosome 9 and is apparently different from previous cases when characterized by the fluorescence in situ hybridization technique. The major differences included duplication of beta-satellite and satellite III DNA sequences and bands 9q13-->q21.1, without duplication or inversion of the alphoid sequences. Based on the reported cases, at least four types of variations can be accounted for. A variety of mechanisms have been proposed to describe the origin of a G-positive band within the 9qh region, which appears to be similar when studied by routine cytogenetic techniques but differs by molecular methods. It is hypothesized that the clinical consequences depend upon the size of the G-positive band(s) duplicated, and a genetic inactivation mechanism might have some sort of influence during the so-called heterochromatinization process. It appears that heterochromatin, once thought to be composed of junk DNA, may have some role after all in suppression of gene(s) and/or spreading of inactivation, if genes are embedded within the heterochromatic region. Apparently, the mixture of different types of DNA creating patches of genetic debris have become a fundamental hidden treasure, where genetically active chromatin could be inactivated without dire consequences. The variable nature of heterochromatin has resulted in cytogenetic heteromorphisms of a number of human chromosomes. Their characterization by molecular techniques is becoming imperative, because fetal wastage have occurred in many situations where variant chromosomes were wrongly identified as chromosomal abnormalities.

Chromosome Banding↗