Biomedical subjects

G Stetten

Publications and source records attributed to G Stetten.

At least 37 records · Page 2Linked to original sources

PubMed1997

Immunolocalization of CENP-A suggests a distinct nucleosome structure at the inner kinetochore plate of active centromeres.

The trilaminar kinetochore directs the segregation of chromosomes in mitosis and meiosis. Despite its importance, the molecular architecture of this structure remains poorly understood [1]. The best known component of the kinetochore plates is CENP-C, a protein that is required for kinetochore assembly [2], but whose molecular role in kinetochore structure and function is unknown. Here we have raised for the first time monospecific antisera to CENP-A [3], a 17 kD centromere-specific histone variant that is 62% identical to the carboxy-terminal domain of histone H3 [4,5] and that resembles the yeast centromeric component CSE4 [6]. We have found by simultaneous immunofluorescence with centromere antigens of known ultrastructural location that CENP-A is concentrated in the region of the inner kinetochore plate at active centromeres. Because CENP-A was previously shown to co-purify with nucleosomes [7], our data suggest a specific nucleosomal substructure for the kinetochore. In human cells, these kinetochore-specific nucleosomes are enriched in alpha-satellite DNA [8]. However, the association of CENP-A with neocentromeres lacking detectable alpha-satellite DNA, and the lack of CENP-A association with alpha-satellite-rich inactive centromeres of dicentric chromosomes together suggest that CENP-A association with kinetochores is unlikely to be determined solely by DNA sequence recognition. We speculate that CENP-A binding could be a consequence of epigenetic tagging of mammalian centromeres.

Amino Acid Sequence↗

PubMed1997

Segregation of a familial balanced (12;10) insertion resulting in Dup(10)(q21.2q22.1) and Del(10)(q21.2q22.1) in first cousins.

An interchromosomal insertion in 3 generations of a family was ascertained through two developmentally delayed first cousins. Cytogenetic analysis using G-banding and chromosome painting showed an apparently balanced direct insertion of chromosome 10 material into chromosome 12, ins(12;10)(q15;q21.2q22.1), in the mothers and grandfather of these children. The proposita inherited only the derivative 10 chromosome, resulting in deletion of 10q21.2 --> 22.1 while her cousin inherited only the derivative 12, resulting in duplication of 10q21.2 --> 22.1. A comparison of the proposita with published deletion cases suggests a pattern of anomalies attributable to deletion of the 10q21 --> q22 region: developmental delay, hypotonia, a heart murmur, telecanthus, broad nasal root and ear abnormalities. This is the first report of a nontandem duplication of the 10q21 --> q22 region. The phenotype of the cousin with the duplication does not overlap greatly with published tandem 10q duplications. Finally, this report reaffirms the importance of obtaining family studies of patients with interstitial chromosomal abnormalities.

Chromosomes, Human, Pair 10↗

PubMed1997

A paternally derived inverted duplication of 7q with evidence of a telomeric deletion.

We report on a de novo constitutional rearrangement involving the long arm of chromosome 7 in a second trimester fetus with the karyotype of 46,XX, inv dup del (7)(pter-q36::q36-q21.2:) pat. Both a large duplication (q21.2-q36) and a small deletion (within q36) were confirmed by FISH studies. DNA analysis on the family showed that the abnormal chromosome was derived from a single paternal homolog. A mechanism is proposed in light of this finding. The phenotype at autopsy was consistent with reported cases of similar duplications in chromosome 7 in that hydrocephalus, a depressed nasal bridge, low set ears, microretrognathia and a short neck were present.

Abortion, Therapeutic↗

PubMed1996

Incidence and significance of chromosome mosaicism involving an autosomal structural abnormality diagnosed prenatally through amniocentesis: a collaborative study.

Among 179,663 prenatal diagnosis cases collected from ten institutions and two publications, 555 (0.3 per cent) were diagnosed as having chromosome mosaicism. Of these, 57 (10.3 per cent) were mosaic for an autosomal structural abnormality, 28 (5 per cent) for a sex chromosome structural abnormality, and 85 (15.3 per cent) were mosaic for a marker chromosome. Ninety-five cases of prenatally diagnosed mosaicism with a structural abnormality in an autosome and a normal cell line, and with a known phenotypic outcome, were collected for karyotype-phenotype correlations through our collaboration (40 cases), a prior survey (26 cases), and published reports (29 cases). They included 13 balanced reciprocal translocations, one unbalanced reciprocal translocation, four balanced Robertsonian translocations, four unbalanced Robertsonian translocations, four inversions, 17 deletions, three ring chromosomes, 19 i(20q), seven +i(12p), six other isochromosomes, and 17 partial trisomies resulting from a duplication or other rearrangement. All cases mosaic for a balanced structural rearrangement resulted in a normal phenotype. All cases of 46/46,i(20q) resulted in normal liveborns. Five of seven cases with 46/47,+i(12p) had an abnormal phenotype compatible with Killian-Pallister syndrome. The overall risk for an abnormal outcome for a mosaic case with an unbalanced structural abnormality, excluding 46/46,i(20q) and 46/47,+i(12p), is 40.4 per cent. In the same category, the study also suggested a correlation between the percentage of abnormal cells and an abnormal phenotype. For mosaicism involving a terminal deletion, the possibility of a familial fragile site should be considered.

Amniocentesis↗

PubMed1996

Ambiguous genitalia in an elderly woman with a mosaic 45,X/46,X,dic(Y)(Q11.2) karyotype.

A 66-year-old woman presented with clitoromegaly since childhood, primary amenorrhea, no breast development, and a large right inguinal hernia. A mosaic karyotype was identified containing a predominant 45,X cell line and a cell line with 46 chromosomes, one X chromosome, and a small dicentric Y chromosome with a breakpoint in band qII.2. The patient underwent hysterectomy, bilateral gonadectomy, inguinal hernia repair, clitoral recession, and formation of a neointroitus. A dysgerminoma was identified in the right dysgenetic gonad. This report demonstrates the natural history of untreated mixed gonadal dysgenesis and the importance of early evaluation and treatment, as well as the molecular characterization of a dicentric Y chromosome.

Aged↗

PubMed1996

Alterations of yeast artificial chromosome transgenic sequences in stretched embryonic stem-cell chromatin visualized by fluorescence in situ hybridization.

Transgenic mice have been generated from embryonic stem (ES) cells carrying functional genes cloned within yeast artificial chromosomes (YACs). Information on the integrity and organization of the inserted sequences, including the number of copies and their orientation to each other, is still limited by current methods. We have applied fluorescence in situ hybridization to stretched chromatin preparations from YAC-transfected ES cells to analyze the organization and copy number of the integrated sequences.

Animals↗

PubMed1995

TRPC1, a human homolog of a Drosophila store-operated channel.

In many vertebrate and invertebrate cells, inositol 1,4,5-trisphospate production induces a biphasic Ca2+ signal. Mobilization of Ca2+ from internal stores drives the initial burst. The second phase, referred to as store-operated Ca2+ entry (formerly capacitative Ca2+ entry), occurs when depletion of intracellular Ca2+ pools activates a non-voltage-sensitive plasma membrane Ca2+ conductance. Despite the prevalence of store-operated Ca2+ entry, no vertebrate channel responsible for store-operated Ca2+ entry has been reported. trp (transient receptor potential), a Drosophila gene required in phototransduction, encodes the only known candidate for such a channel throughout phylogeny. In this report, we describe the molecular characterization of a human homolog of trp, TRPC1. TRPC1 (transient receptor potential channel-related protein 1) was 40% identical to Drosophila TRP over most of the protein and lacked the charged residues in the S4 transmembrane region proposed to be required for the voltage sensor in many voltage-gated ion channels. TRPC1 was expressed at the highest levels in the fetal brain and in the adult heart, brain, testis, and ovaries. Evidence is also presented that TRPC1 represents the archetype of a family of related human proteins.

Adult↗

PubMed1995

An accessory marker derived from chromosome 20 and its co-existence with a mosaic trisomy 20 cell line.

We report a 16-month-old boy with delayed psychomotor development, dysmorphic features, and failure to thrive. He had a mosaic karyotype detected prenatally: mos 46,XY/47,XY, +r(20)/47,XY, +20. After birth, the abnormal cell lines were confirmed in a number of tissues. The small ring chromosome was identified using fluorescence in situ hybridization as derived from chromosome 20. We compared our patient with previously reported cases of mosaic trisomy 20 detected prenatally and associated with an abnormal phenotype. In an attempt to characterize an r(20) syndrome, we also compared our case with two similar reports in the literature.

Cell Line↗

PubMed1995

Molecular characterization of a deleted X chromosome (Xq13.3-Xq21.31) exhibiting random X inactivation.

As a result of selection following random X chromosome inactivation in human females, X chromosomes with visible deletions are usually inactive in every somatic cell. We have studied a female with mental retardation and dysmorphic features whose karyotype includes an X chromosome with a visible interstitial deletion in the proximal long arm. Based on cytogenetic analysis, the proximal breakpoint appeared to be in band Xq13.1, and the distal one in band q21.3. However, molecular analyses show that less of the q13 band is missing than cytogenetic studies indicated, as the deletion includes only loci from the region Xq13.3 to Xq21.31. Unexpectedly, studies of chromosome replication show that the pattern of X inactivation is random. Whereas the deleted X chromosome is late replicating in some cells from all tissues studied, it is early replicating in the majority of blood lymphocytes and skin fibroblasts, and is the active X chromosome in many of the hybrids derived from skin fibroblasts. As this chromosome is able to inactivate, it must include those DNA sequences from the X-inactivation center (XIC) that are essential for cis X inactivation. Molecular studies show that the XIC region, at Xq13.2, is present, so it is unlikely that the lack of consistent inactivation of this chromosome is attributable to close proximity of the breakpoint to the XIC. Supporting this conclusion is the similarity of the breakpoints to those of the other chromosomes we studied, whose deletions clearly do not interfere with the ability to inactivate. Our results show that deletions distal to DXS441 in Xq13.2 do not interfere with cis X inactivation. We attribute the random pattern of X inactivation reported here to the fact that in the tissues studied, cells with this interstitial deletion are not at a selective disadvantage.

Adolescent↗

PubMed1995

Magnetic orientation of spiny lobsters in the ocean: experiments with undersea coil systems

The western Atlantic spiny lobster Panulirus argus undergoes an annual migration and is also capable of homing to specific dens in its coral reef environment. Relatively little is known, however, about the orientation cues that lobsters use to guide their movements. To determine whether lobsters can orient to the earth's magnetic field, divers monitored the orientation of lobsters tethered inside magnetic coil systems submerged offshore in the Florida Keys, USA. Each coil could be used to reverse either the horizontal or vertical component of the earth's field. Tethered lobsters walking inside the coils often established and maintained consistent courses towards specific directions. After a lobster had established a course, it was exposed to one of three conditions: (1) a reversal of the horizontal component of the earth's field; (2) a reversal of the vertical component of the earth's field; or (3) no change in the ambient field (controls). Lobsters subjected to the horizontal field reversal deviated significantly from their initial courses. In contrast, control lobsters and those subjected to the reversed vertical field did not. These results demonstrate that spiny lobsters possess a magnetic compass sense. Because inverting the vertical component of the earth's field had no effect on orientation, the results suggest that the lobster compass is based on field polarity and thus differs from the inclination compasses of birds and sea turtles. The magnetic compass of lobsters may function in homing behavior, in guiding the autumn migration or in both.

Journal Article↗

PubMed1994

Molecular analysis of a complex chromosomal rearrangement and a review of familial cases.

A complex chromosome rearrangement (CCR) involving chromosomes 7, 8, and 13 was detected in a phenotypically normal woman ascertained through her mentally retarded son with abnormal phenotype. He had a karyotype with 47 chromosomes including an extra der(13). In initial banding studies the CCR in the mother was interpreted as a three-way translocation. Fluorescence in situ hybridization with whole chromosome libraries and a telomere-specific probe was used to better characterize the rearrangement. Combined data allowed us to reinterpret the CCR as a translocation and an insertion. A review of 35 familial CCRs involving at least three chromosomes led to the following observations: 1) familial CCRs tend to have fewer chromosomes involved and fewer break-points than do de novo CCRs; 2) familial transmission is mainly observed through female carriers although the origin of de novo cases is paternal; 3) an apparent excess of balanced female carriers among the offspring of index carriers was noted; and 4) meiotic segregation resulting in malformed liveborn infants is most frequently due to adjacent-1 segregation, followed by 4:2 segregation; no adjacent-2 segregation was observed.

Abnormalities, Multiple↗

PubMed1994

Unilateral renal hypoplasia and contralateral renal agenesis: a new association with 45,X/46,XY mosaicism.

The association of urinary anomalies with Turner's syndrome is well established. This report describes an unusual antenatal presentation of this cytogenetic disorder and the first reported case of unilateral renal hypoplasia and contralateral renal agenesis in a 45,X/46,XY fetus. The fetus presented with severe third trimester oligohydramnios and symmetrical intrauterine growth retardation at 29 weeks and 2 days' gestation. Chorionic villus cultures revealed a 45,X karyotype. A phenotypically male infant weighing 1833 g was delivered at 35 weeks and 2 days. Chromosomal analysis of the newborn showed a 45,X/46,XY mosaicism, and surgical exploration revealed absence of the left kidney and a hypoplastic right kidney. The infant died at 11 months of age from renal failure and peritonitis. This case demonstrates that monosomy X may be encountered in fetuses with marked growth delay and oligohydramnios. The etiology of the oligohydramnios in this case was a fetal renal malformation not previously described in Turner's syndrome. Antenatal cytogenetic findings should be confirmed postnatally, with a search for mosaicism, when monosomy X is encountered.

Female↗

PubMed1994

Nonrandom inactivation of the Y-bearing X chromosome in a 46,XX individual: evidence for the etiology of 46,XX true hermaphroditism.

We previously reported a subject with 46,XX true hermaphroditism who had a 46,X,del(X) karyotype and Y-chromosomal sequences in genomic DNA. We hypothesized that the Y-chromosomal sequences were translocated to the deleted X chromosome and that the incomplete testis determination of this individual was the result of inactivation of the translocated X chromosome. In situ hybridization studies demonstrated that the Y-chromosomal sequences were located on the distal portion of the short arm of the deleted X chromosome. Investigation of the replication of the X chromosome, using a modified R-banding technique and localization of Y-chromosomal sequences by in situ hybridization, showed that the translocated X chromosome was late replicating in all 100 EBV-transformed lymphoblasts that were examined. By contrast, when cells from a subject with 46,XX maleness were studied, the translocated X chromosome was late replicating in only 21 of 47 cells. As the late-replicating X chromosome is presumed to be the inactive X chromosome, selection of cells in which the Y-bearing X chromosome has been inactivated may play a role in the incomplete testis determination in subjects with "Y-positive" 46,XX true hermaphroditism.

Chromosome Mapping↗

PubMed1993

Unbalanced translocation, t(18;21), detected by fluorescence in situ hybridization (FISH) in a child with 18q- syndrome and a ring chromosome 21.

We report on an 8-year-old girl with minor anomalies consistent with 18q- syndrome and mild developmental delay. Initially cytogenetics showed a terminal deletion of chromosome 21 with mosaicism for a small ring chromosome 21 as the only apparent karyotypic abnormality: mos 45,XX,-21/46,XX,+r(21) (48%/52%). Further studies including FISH and DNA analysis demonstrated a de novo unbalanced translocation of chromosomes 18 and 21 with the likely breakpoints in 18q23 and 21q21.1. Most of 21q was translocated to the distal long arm of one chromosome 18, and this derivative 18 appeared to lack 18q23-qter. The small ring chromosome 21 [r(21)], present in only 52% of the patient's blood lymphocytes, did not appear to be associated with the abnormal phenotype since all 13 chromosome 21 markers that were examined in genomic DNA were present in 2 copies, and the phenotype of the patient was consistent with the 18q- syndrome. The karyotype was reinterpreted as mos 45,XX,-18,-21,+der(18) t(18;21) (q23;q21.1)/46,XX,-18,-21,+der(18) t(18;21) (q23;q21.1), +r(21) (p13q21.1) (48%/52%). These results demonstrate the power of FISH in conjunction with DNA analysis for examination of chromosome rearrangements that may be misclassified by traditional cytogenetic studies alone.

Cell Line↗

PubMed1993

A complex chromosomal rearrangement detected prenatally and studied by fluorescence in situ hybridization.

We report of case of a complex chromosomal rearrangement detected prenatally and studied with traditional banding methods and fluorescence in situ hybridization. The combination of these techniques showed that four chromosomes were involved in the translocation. Nine breakpoints were proposed to explain these results. Some of the findings could only be detected with fluorescence in situ hybridization, demonstrating the usefulness of this technique in characterizing chromosomal abnormalities that would otherwise be difficult to interpret correctly with classical cytogenetics alone.

Adult↗

PubMed1993

The role of the sex-determining region Y gene in the etiology of 46,XX maleness.

The condition of 46,XX maleness is characterized by testicular development in subjects who have two X chromosomes but who lack a normal Y chromosome. Several etiologies have been proposed to explain 46,XX maleness: 1) translocation of the testis-determining factor from the Y to the X chromosome, 2) mutation in an autosomal or X chromosome gene which permits testicular determination in the absence of TDF, and 3) undetected mosaicism with a Y-bearing cell line. We evaluated 10 affected subjects who were ascertained for different reasons and who had several distinct phenotypes. Six subjects had inherited sequences from the short arm of the Y chromosome including the sex-determining region Y gene (SRY). Five of the subjects were pubertal at the time of evaluation and had a phenotype similar to that of Klinefelter syndrome with evidence of Sertoli cell and Leydig cell dysfunction. One subject had evidence from Southern blot analysis and in situ hybridization for the presence of an intact Y chromosome in approximately 1% of cells. Three subjects lacked Y sequences by Southern blot analysis and by polymerase chain reaction amplification of SRY. These subjects were ascertained in the newborn period because of congenital anomalies. One had multiple anomalies including cardiac abnormalities; one had cardiac anomalies alone; and one had ambiguous genitalia. Our data confirm the genetic heterogeneity of 46,XX maleness, in which some subjects have SRY while other subjects lack it. In addition, there is phenotypic heterogeneity among subjects who lack SRY suggesting that there is also genetic heterogeneity within this subgroup.

DNA Restriction Enzymes↗

PubMed1993

Prenatal cytogenetic analysis of the fetus.

A number of different cell sources can be used for prenatal cytogenetic analysis, the most common being chorionic villi and amniotic fluid. Analysis can be done at any time between 9 weeks' gestation and term. Depending on the cell source and type of analysis required, the laboratory will take anywhere from 24 hours to 2 weeks to complete the study.

Amniotic Fluid↗

PubMed1992

Prenatal identification of small mosaic markers of different chromosomal origins.

In situ hybridization using a series of alphoid DNA probes has demonstrated the origin of two small accessory mosaic marker chromosomes ascertained from 1079 amniocenteses. These markers appeared to be de novo, derived from acrocentric chromosomes, and identical by traditional cytogenetic staining (G, Q, C, AgNOR, Hoechst-distamycin). Molecular characterization showed that one marker had originated from chromosome 14, the other from chromosome 22. Clinical outcome in both cases was normal.

Adult↗