Rett syndrome and fragile site in Xp22.
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Autistic Disorder↗
Biomedical subjects
N Archidiacono
Publications and source records attributed to N Archidiacono.
Cytologic demonstration of differential activity of rRNA gene clusters in different human tissues.
rRNA gene activity was evaluated by cytologic methods in cultured human cells from two different tissues grown under controlled experimental conditions. The modal and average numbers of silver positive nucleolus organizers (NOs) per cell as well as the distribution of cells with different numbers of silver positive NOs and different combinations of D- plus G-group silver stained chromosomes, were evaluated. Statistically significant differences in the average number of silver positive NOs per cell between leukocytes and fibroblasts grown under standard experimental conditions have been demonstrated. The observed differences became sharper in cells cultured under more restrictive conditions. Also, differences in the frequency of silver positivity of specific chromosomal NOs located on individually identified chromosomes were observed in cells from the same tissue. Furthermore, differences in the frequency of activation of rDNA clusters located on the same chromosome were also observed between cells from the two tissues. The possible biologic meanings of these findings are discussed.
Cells, Cultured↗
Hormone-modulated rRNA gene activity is visualized by selective staining of the NOs.
The role of Growth Hormone and Dexamethasone in the regulation of rRNA gene activity was evaluated on cultured human fibroblasts by the cyto-chemical method of selective silver staining. By this method the transcriptionally active r-gene clusters can be specifically visualized in individual cells. Statistically significant increases in the rate of rRNA transcriptional activity were demonstrated after hormone administration.
Adult↗
The transcriptional activity of individual ribosomal DNA gene clusters is modulated by serum concentration.
The activity of ribosomal gene clusters has been studied by cytological methods in human cultured cells grown in different amounts of serum under controlled experimental conditions. It has been shown that increasing amounts of serum induce an increase in ribosomal RNA synthesis at the single cell level. Furthermore, the concomitant identification of individual rRNA gene clusters by fluorescent techniques allowed us to demonstrate: (1) that individual gene clusters have differential transcriptional activity and differential frequency of activation; (2) that ribosomal gene activity is closely associated with the amount of silver-positive gene product and; (3) that environmental variations modulate rRNA synthesis by repressing or derepressing specific gene clusters.
Blood↗
Genes controlling gp25/30 cell-surface molecules map to chromosomes X and Y and escape X-inactivation.
The monoclonal antibody AbO13 defines a cell-surface antigen that is expressed on most cultured human cells, but not on rodent cells. AbO13 precipitates glycoproteins of 25,000 and 30,000 mol. wt. from lysates of [3H]glucosamine-labeled human cells. Results of the serological typing of a panel of 25 rodent-human somatic cell hybrid clones show that reactivity with AbO13 segregates with the human X and Y chromosomes. The presence of either of these chromosomes is sufficient for O13 expression on the hybrid cell surface. Analysis of hybrid clones containing human X chromosomes with karyotypically defined deletions permitted the regional assignment of the X-linked gene locus controlling the expression of O13 to Xp22-pter. In addition, AbO13 is reactive with Chinese hamster-human hybrids derived from fibroblasts of a 49,XXXXX individual that contained only inactivated copies of the human X chromosome. These results suggest that the X-linked locus determining the expression of O13 is not subject to X-inactivation.
ABO Blood-Group System↗
A prenatally detected inv dup(15).
An extra G group-like chromosome was found in an amniotic fluid cell culture. With multiple banding techniques it was identified as inv dup(15). BUdR incorporation was used to determine the lateral asymmetry of the marker, which consisted of 2 distal spots arranged contralaterally, consistent with DNA polarity conservation in chromosome rearrangements.
Adult↗
Cytological mapping of the human glucose-6-phosphate dehydrogenase gene distal to the fragile-X site suggests a high rate of meiotic recombination across this site.
The human gene for glucose-6-phosphate dehydrogenase (G6PD) has been subregionally mapped to band Xq28 by segregation analysis in rodent-human somatic cell hybrids [Pai, G. S., Sprinkel, J. A., Do, T. T., Mareni, C. E. & Migeon, B. R. (1980) Proc. Natl. Acad. Sci. USA 77, 2810-2813]. We have previously reported a common type of X-linked mental retardation associated with an inducible fragile site at Xq27-Xq28 segregates in a close linkage relationship with a G6PD variant, but the relative position of G6PD with respect to the fragile site has not yet been established. This fragile-X syndrome has been shown to be closely linked also to a Taq I restriction fragment length polymorphism detected by a cDNA probe for factor IX, and the latter locus has been mapped to the subtelomeric region Xq26-Xq28 [Camerino, G., Mattei, M. G., Mattei, G. F., Jaye, B. & Mandel, J. L. (1983) Nature (London) 306, 701-704]. The in situ hybridization studies reported here provide strong evidence that G6PD is located on the Xq telomeric fragment distal to the fragile site. These observations and the well-established knowledge that the genes for Deutan and Protan colorblindness are closely linked to G6PD, but segregate independently of factor IX deficiency, suggest that the fragile site associated with this type of X-linked mental retardation occurs in a region prone to high frequency of meiotic recombination.
Animals↗
A young girl with ring(18) mosaicism: cytogenetic studies and PEP A mapping.
A young girl with 46,XX,r(18)/46,XX/45,XX,-18 chromosome constitution is reported. She displays a slight degree of mental retardation. The line with the ring chromosome predominates in blood lymphocytes. In skin fibroblast culture the ring(18) line showed a constant decreasing trend, from 45% at the first passage, down to its disappearance at the 19th passage, where only 46,XX cells were observed. The child/mid parents' ratio of Peptidase A activity in red cells was 0.36. The Peptidase A activity in a fibroblast clone 46,XX,r(18) was 0.55 compared to the 46,XX line. These data suggest that the PEP A locus was lost in ring formation.
Adolescent↗
Treated glass coverslips for in situ culture of amniotic cells: better cell adhesion and growth than on plastic.
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Amnion↗
Brief report: linkage between G6PD and fragile-X syndrome.
Eighteen Sardinian pedigrees segregating for the X-fragile site syndrome were studied with respect to the segregation of the fragile site (FS) at Xq28, mental retardation, and macro-orchidism. No exception was found in the association of this symptomatic triad (MOM-X) in 41 out of 42 patients examined. The exceptional individual had micro- rather than macro-orchidism and was found to have a 47, XXY sex chromosome complement. In six informative sibships, the MOM-X syndrome was found to segregate in close linkage association with G6PD-deficiency or protan colorblindness. The maximum likelihood estimate of recombination if 6% with 90% fiducial limits between 2.5 and 19.5% and an odds ratio in favor of measurable linkage of 428:1. However, no hint of measurable linkage was found in six pedigrees segregating for G6PD and the Renpenning syndrome or other unspecified types of X-linked mental retardation. These data give strong support to the generally held hypothesis that the FS at Zq28, characteristic of the MOM-X syndrome, is a direct expression of a genetic change in the same chromosomal region. They also clearly suggest that X-linked MR without FS may be the result of different allelic mutations at the same locus.
Color Vision Defects↗
X chromosome replication patterns in a case of X;9 balanced translocation.
A case of X;9 balanced translocation in a female with amenorrhoea is reported. The X breakpoint was at Xq21, inside the 'critical region'. The normal X was consistently late replicating in blood lymphocytes and skin and ovary fibroblasts.
Adult↗
Characterization of normal and rearranged human chromosomes by simultaneous Q- and R-banding with chromomycin A3.
Simultaneous Q- and R-type banding patterns in human chromosomes have been achieved by staining with chromomycin A3. Some peculiarities of these patterns as compared to the patterns induced by other fluorochromes are described. The resolution power of this technique in analyzing structural rearrangements of human chromosomes is discussed.
Chromomycin A3↗
X pentasomy: a case and review.
A 49,XXXXX girl is reported. The most typical features of the patient are: severe mental retardation, serious dental anomalies, various anomalies of the bones, and a high rate of gonadotropins. The few similar cases so far described are reviewed to aid in delineation of this rare syndrome. The implications of Lyon's hypothesis on X-aneuploidies are also discussed.
Aneuploidy↗
Extra small metacentric chromosome identified as i(18p).
A case of a supernumerary metacentric small chromosome, diagnosed at birth, is described. The cytogenetic findings support its identification as i(18p). The clinical development from birth to 12 months is reported, with particular attention given to the psychomotor retardation and to the immunological aspect.
Chromosome Aberrations↗
Additional pedigree supporting the frequent origin of XXYY from consecutive meiotic non-disjunction in paternal gametogenesis.
A 48,XXYY Sardinian patient, born to a 46,XX mother heterozygous for the Gd Mediterranean mutant, and to a 46,XY father hemizygous for the same mutant, was found to have a mosaic distribution of G6PD(+) and G6PD(-) peripheral red blood cells. The most likely interpretation of this finding is that the propositus is an additional example of an XXYY zygote derived from a consecutive meiotic non-disjunction during paternal gametogenesis.
Adult↗
Trisomy 20p from maternal t(3;20) translocation.
A case of trisomy 20p resulting from a maternal translocation t(3;20) is described. QM and BUdR banding techniques were used for its identification. A round face with oblique palpebral fissures, strabismus, cardiac and vertebral abnormalities, mild psychomotor retardation, together with poor coordination and speech impediment, are the most typical features of the proband.
Child, Preschool↗
t(9/22) with centric fission and NOR translocation leading to a case of pure 9p trisomy in the offspring.
A case of trisomy 9p originating from t(9/22) mat is reported. The rearrangement is characterized by centric fission of chromosome 9 and by translocation of NOR from chromosome 22 to 9q. The hypothesis of centric fission is discussed on the basis of various banding patterns. The case also reveals unusual knee dislocation.
Cell Nucleolus↗
Nucleolus organizer and N-band distribution in morphologic and fluorescence variants of human chromosomes.
Three cases of morphologic variants of human D- or G-group chromosomes have been studied by N- and Ag-AS banding techniques. The results confirm our previous findings about the localization of nucleolus organizers on the secondary constrictions of acrocentric chromosomes. Preliminary results on the distribution and number of N bands in D- and G-group chromosomes with morphologic and fluorescence variants are reported.
Cell Nucleolus↗