Loss of the Y chromosomal PAR2-region in four familial cases of satellited Y chromosomes (Yqs)

Applying fluorescence in-situ hybridization (FISH) of various Y chromosomal DNA probes to four familial cases of human Yqs, it was possible to demonstrate that the formation of Yqs must have arisen from a reciprocal translocation involving the short arm of an acrocentric autosome and the heterochromatin of the long arm of the Y chromosome (Yqh). Breakpoints map within Yqh and the proximal short arm of an acrocentric autosome resulting in the gain of a nucleolus organizer region (NOR) including the telomere repeat (TTAGGG)n combined with the loss of the pseudoautosomal region 2 (PAR2) at the long arm of the recipient Y chromosome. In no case could the reciprocal product of an acrocentric autosome with loss of the NOR and gain of PAR2 be detected. Using the 15p-specific classical satellite-III probe D15Z1 in two of the four Yqs probands presented here, it could be shown that the satellited material originated from the short arm of chromosome 15. In contrast to the loss of PAR2 in Yqs chromosomes, another Y chromosomal variant (Yqh-) showing deletion of long-arm heterochromatin in Yq12 has retained PAR2 referring to an interstitial deletion of Yq heterochromatin in such deleted Y chromosomes.

A prospective controlled study of karyotyping for 430 consecutive babies conceived through intracytoplasmic sperm injection

OBJECTIVE

To compare the karyotype of babies conceived through ICSI with that of naturally conceived babies.

DESIGN

Prospective controlled study.

SETTING

The Egyptian IVF-ET Center, Cairo, Egypt.

PATIENT(S)

Four hundred and thirty babies conceived through ICSI and 430 babies conceived naturally.

INTERVENTION(S)

ICSI and karyotyping.

MAIN OUTCOME MEASURE(S)

Abnormal karyotype.

RESULT(S)

Four hundred and thirty consecutive babies conceived through ICSI who were delivered in one hospital had 15 abnormal karyotypes (3.5%). Of the 15 babies, 7 were of female phenotype and 8 of male phenotype. Six babies had sex chromosome anomalies, 8 had autosomal anomalies, and 1 had combined sex chromosome and autosomal anomalies. A control group of 430 consecutive babies conceived naturally who were delivered in one hospital had no abnormal karyotype. The difference between the two groups was significant (P<.001).

CONCLUSION(S)

ICSI carries a small but significant increased risk of abnormal karyotyping to the offspring. This risk appears to be equally distributed between autosomal and sex chromosome anomalies.

Increased incidence of numerical chromosome abnormalities in spermatozoa injected into human oocytes by ICSI

The potential risk of transmitting chromosomally abnormal spermatozoa from infertile males into oocytes through intracytoplasmic sperm injection (ICSI) has prompted us to investigate the male pronuclei of tripronuclear zygotes (3PN) obtained after ICSI. To specify the type of anomalies, we used triple colour fluorescent in-situ hybridization (FISH) with three specific probes for chromosomes X, Y and 18. From a total of 163 paternal complements of ICSI-3PN zygotes, 90 (55.2%) had Y-chromosome signals. Eighty-three of these were normal, four had the disomy XY and three were diploid. In the remaining 73 ICSI-3PN zygotes without Y-chromosome signals, the origin of paternal pronuclei was extrapolated through chromosome constitution of the first polar body. Five anomalies were found in this group of zygotes, giving a total rate of numerical chromosome aberrations for fertilizing spermatozoa of 7.4%. In contrast to ICSI, only two disomies (1.5%) were found in the control group of IVF-3PN zygotes. Compared with the incidence of chromosome anomalies between paternal-derived pronuclei of ICSI- and IVF-3PN zygotes, the difference was statistically significant (P < 0.025). This study provides the first direct evidence of a higher incidence of numerical chromosome anomalies in sperm-fertilized human oocytes after ICSI.

Current understanding of androgenetic alopecia. Part I: etiopathogenesis

Androgenetic alopecia (AGA) is the most common type of hair loss in men and women. This continuous process results in a type of alopecia that follows a definite pattern in those individuals who are genetically predisposed. At present the predisposing genes are unknown but the relatively strong concordance of the degree of baldness in fathers and sons is not consistent with a simple Mendelian trait and a polygenic basis is therefore most likely. AGA can be defined as a DHT-dependent process with continuous miniaturization of sensitive HF. Today we do not understand the molecular steps involved in androgen-dependent beard growth versus androgen-dependent hair loss in AGA. However, recent experimental and clinical advances enable us to explain some pathogenetic steps leading to androgenetic hair loss. Among other steroidogenic isoenzymes such as 17b- and 3b- hydroxysteroid dehydrogenases, the type 2 5a-reductase within the dermal papilla plays a central role by the intrafollicular conversion of T to DHT.

Intracytoplasmic sperm injection: what are the risks?

Intracytoplasmic sperm injection, a relatively new technique used at the time of in vitro fertilization to fertilize human oocytes, has provided couples with very severe male factor infertility the ability to conceive their own biologic children. Many men with severe oligospermia or azoospermia can now pass their genes on to their progeny, an event that might not have been possible for them just a few years ago. Recent studies now suggest that there may be genetic and developmental differences in some children conceived through intracytoplasmic sperm injection. It is likely that genetic testing and counseling will be recommended for all couples with male factor infertility in the near future.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader will be able to describe the various indications for the use of ICSI in the treatment of infertility, to identify the potential long-term risks associated with the use of ICSI, and to estimate the rate of chromosomal abnormalities in this population of infertile patients.

Exclusion of PPEF as the gene causing X-linked juvenile retinoschisis

X-linked juvenile retinoschisis (RS) is a progressive vitreoretinal degeneration localised in Xp22.1-p22.2. A human homologue of the retinal degeneration gene C (rdgC), a gene that in Drosophila melanogaster prevents light-induced retinal degeneration, was localised in the RS obligate gene region. We have tested the gene, designated PPEF in humans, as a candidate gene in RS patients using RT-PCR and the protein truncation test on RNA and SSCP on DNA. No mutations were identified, making it highly unlikely that PPEF is the gene implicated in RS. The data presented facilitate mutation analysis of the PPEF gene in other diseases which have been or will be localised to this region.

Sex chromosomal anomalies in pregnancies conceived through intracytoplasmic sperm injection: a case for genetic counselling

The prevalence of sex chromosomal anomalies (SCA) is higher after treatment with intracytoplasmic sperm injection (ICSI) than in naturally conceived pregnancies. This finding is not only important in the debate about the genetic safety of ICSI, it also has repercussions on the design of appropriate strategies for prenatal and preimplantation diagnosis in ICSI pregnancies. We discuss here in detail the developmental prognosis of individuals carrying a sex chromosomal anomaly. Major malformations do occur in Turner syndrome, but not so in Klinefelter, the triple X and the XYY syndromes. Infertility represents an almost obligate finding in Klinefelter syndrome, but the latest developments in microassisted reproduction may help to overcome this problem. Importantly, mental retardation does not occur more often in individuals with an SCA than in normal controls. Academic achievement, however, may be somewhat reduced compared with peers. Overall, for most children carrying a sex chromosomal anomaly, a major congenital handicap is not to be expected, and the long-term developmental prognosis is fairly good. Therefore, if an SCA is diagnosed prenatally in an ICSI pregnancy, an unbiased and detailed discussion of the developmental perspectives is warranted. The option of continuing such a pregnancy should be given due consideration.

New domains of neural cell-adhesion molecule L1 implicated in X-linked hydrocephalus and MASA syndrome

The neural cell-adhesion molecule L1 is involved in intercellular recognition and neuronal migration in the CNS. Recently, we have shown that mutations in the gene encoding L1 are responsible for three related disorders; X-linked hydrocephalus, MASA (mental retardation, aphasia, shuffling gait, and adducted thumbs) syndrome, and spastic paraplegia type I (SPG1). These three disorders represent a clinical spectrum that varies not only between families but sometimes also within families. To date, 14 independent L1 mutations have been reported and shown to be disease causing. Here we report nine novel L1 mutations in X-linked hydrocephalus and MASA-syndrome families, including the first examples of mutations affecting the fibronectin type III domains of the molecule. They are discussed in relation both to phenotypes and to the insights that they provide into L1 function.

Investigation of the activation state of the X chromosome in non-Hodgkin's lymphomas

Cytogenetic analysis of non-Hodgkin's lymphomas (NHLs) has previously revealed a high incidence of numerical abnormalities involving the X chromosome. We have now used a combination of fluorescence in situ hybridization (FISH) and Southern blot analysis of methylation to examine the activation state of additional X chromosomes in NHL. Although FISH analysis of X chromosome centromeres in interphase nuclei was complicated by a number of factors, such as cell-cycle position, there was evidence that more than one X chromosome was present in the active state in 4/9 NHL. Methylation studies were carried out using the M27 beta probe, which also suggested that more than one activated X chromosome was present in at least 2/7 NHL cases. The two approaches therefore provided evidence that in some cases of NHL, unlike sex-chromosome-syndrome individuals, additional X chromosomes may be present in the active state. These data support the suggestion that NHL-associated oncogenes might be located on the X chromosome.

Sex chromosomal abnormalities. Etiology, phenotypic expression, and the role of lyonization

Individuals with sex chromosomal abnormalities have significantly better chances of leading normal lives than individuals with autosomal abnormalities. This is due, in part, to the role of lyonization in the genetic inactivation of X chromosomes. In contrast to earlier studies contaminated with subject ascertainment bias, prospective studies of individuals with SCA generally indicate a relatively normal profile with respect to overall intellectual capacity and psychopathology. Although some SCAs affect neuromotor, speech, language, cognitive and emotional development to some degree, it is noteworthy that none of the effects necessarily occurs and that some of the deficits are amenable to corrective intervention. Results from prospective studies also indicate significant genotype-environment interactions that can have important implications for intervention.

Fragile X expression in Martin-Bell syndrome, intellectually normal individuals, and neoplasia, interpreted by a viral hypothesis

We present data on fragile X expression in lymphocytes obtained from the following patients: a university student, an infertile couple, 6 of 22 prostatic cancer patients, a meningioma patient, and members of families with meningioma and familial gliomas. All patients were of normal intelligence. In addition, we report 3 cases of central nervous system (CNS) tumors in more typical fragile X families. We suggest that the fragile X expression as well as the clinical findings may be caused by a viral (or similar) infection. The virus may require a receptor protein coded by one allele of a gene on the X chromosome.

Paternal contributions to birth defects

The question of the extent of paternal contributions to birth defects and adverse reproductive outcomes gained new urgency with the concerns of Vietnam veterans exposed to Agent Orange. There is well-established evidence for the occurrence of certain autosomal dominant sporadic mutations in the offspring of older fathers. Paternal nondisjunction at meiosis or mitosis accounts for a significant proportion of chromosomal errors such as trisomy 21. Certain chromosomal abnormalities in males also contribute to adverse reproductive outcomes in relation to repetitive spontaneous abortion and infertility. The question of whether or not teratogens can act through the male is complex. While certain suggestive evidence is reviewed here, conclusive data are yet to be found. Yet, we must remember that it was not long ago that the placenta was assumed to be an impenetrable barrier between mother and fetus. This field is ripe for further well-designed and careful investigation.

Does melatonin deficiency cause the enlarged genitalia of the fragile-X syndrome?

Melatonin profiles were studied in five males with cytogenetic and clinical features of the fragile-X syndrome including megalo-orchidia and macrogenitosomia. In comparison with age-matched normal controls, the fragile-X group showed lower melatonin values and a significant impairment of the nocturnal rise in this hormone. Melatonin deficiency may thus be responsible for some of the phenotypic features of this disorder.

Müllerian dysgenesis

The multifaceted syndrome of müllerian dysgenesis appears to represent a defect in mesodermal organization and is often associated with renal and skeletal anomalies. This report discusses the embryology, multifactorial etiology, clinical presentation and management of the syndrome from a historical standpoint and details our experience with 35 affected patients. Both Frank dilatation and McIndoe vaginoplasty appear to be acceptable means of therapy. The therapeutic success depends to a large extent on the psychosocial adaptation of the patient.

Effects of post-irradiation interval on translocation frequency in male mice

Hybrid male mice were given 5 Gy + 5 Gy acute X-rays 24 h apart, with cytological examination of testes 16-19, 39-42 and 64-66 weeks later. Mean testis weights were significantly lower in the youngest group than in the other two. However, translocation frequencies in spermatocytes of the youngest group (mean of 0.57 per cell) were significantly higher than in either of the other two groups, which gave similar values averaging 0.36 translocations per cell. There was highly significant heterogeneity in translocation yields within the youngest group. The decline in translocation yield with time after irradiation is in line with that reported by Léonard and Deknudt (1970) in inbred strain C57BL males. Analysis of all available data suggests that high translocation yields are found during late stages in the process of germ-cell repopulation of the testis after high radiation doses and may be connected with changing frequencies of radiosensitive and radioresistant stem cell populations as repopulation proceeds.

Two new X-autosome translocations in the mouse

The reciprocal translocations T(X;4)37H and T(X;11)38H were induced by acute X-irradiation of spermatozoa. Male heterozygotes are completely aspermic with a spermatogenic block at pachytene and testis masses about one third of normal, though metaphase I is very occasionally reached in T37H. For both translocations the X chromosome breakpoints are in band XA2, and the autosomal breakpoints are in 4D3 for T37H and 11E1 for T38H, leading to long and short marker chromosomes. Chain quadrivalents predominated in oocytes at MI, with no rings; there were 32% trivalent + univalent configurations in T37H and 40% in T38H. These generated (1) XO mice, (2) tertiary trisomics carrying 20 bivalents and the small X4 (T37H) or X11 (T38H) markers. These trisomics were apparently lethal in T37H but sub-viable in T38H and sometimes fertile as XX11 and trisomic XXX11 females, though sterile as XX11Y males. However, many developed exencephaly in utero, probably because of the distal duplication on chromosome 11. No tertiary monosomics were found in 12 to 14 day embryos. Seven percent of all female progeny were XO, with a higher than expected frequency in T37H and a lower than expected one in T38H. T37H is about two units and T38H about five units from the spf locus on the X chromosome with evidence for some crossover suppression between the T38H breakpoint and Ta. Autosomal linkages found were T37H-m-b (R.F. of 16 +/- 4% between T37H and m) and T38H-Rewc (R.F. of 5 +/- 3%). T37H/+ females weighed about 10% less than normal females at birth and about 30% less at weaning; there was little if any effect in T38H/+ females or in males carrying either translocation. Neither translocation had any marked effect on viability. T37H/+ females showed variegation when heterozygous for b with the wild type allele in the long 4X marker. On average, about 20% of the coat was brown rather than black. However, no clear evidence for m variegation was found.

[A new observation of an H-Y antigen positive 46, XX male (author's transl)]

A new serologic test for detecting the H-Y antigen by indirect fluorescence performed on purified lymphocytes was developed. It allowed us to demonstrate H-Y antigen in an 46, XX male. The presence of this antigen explains why the primitive gonad underwent testicular differentiation. Several mechanisms could account for the presence of H-Y antigen. Mosaicism or translocation of an X on a Y or an autosome may prevent detection of a Y chromosome. Alternatively, a Y chromosome may have disappeared during embryogenesis, The last hypothesis suggests that an autosome may carry a structural gene coding for H-Y antigen; in this case thye Y chromosome would act only as an accessory regulating gene.

Genetic effects of the atomic bombs: a reappraisal

Data are presented on four indicators of genetic effects from studies of children born to survivors of the atomic bombings of Hiroshima and Nagasaki. The indicators are frequency of untoward pregnancy outcomes (stillbirth, major congenital defect, death during the first postnatal weak); occurrence of death in live-born children, through an average of life expectancy of 17 years; frequency of children with sex chromosome aneuploidy; and frequency of children with mutation resulting in an eletrophoretic variant. In no instance is there a statistically significant effect of parental exposure; but for all indicators the observed effect is in the direction suggested by the hypothesis that genetic damage resulted from the exposure. On the basis of assumptions concerning the contribution that spontaneous mutation in the preceding generation makes to the indicators in question, it is possible to estimate the genetic doubling dose for radiation for the first three indicators (the data base is still too small for the fourth). The average of these estimates is 156 rems. This is some four times higher than the results from experimental studies on the mouse with comparable radiation sources, which have been the principal guide to the presumed human sensitivities. The relevance of these data in setting permissible limits for human exposures is discussed briefly.

[The vanishing testis syndrome. Considerations on a case]

The aetiopathogenesis and clinical and diagnostic features of bilateral absence of the testicles in 46XY subjects are briefly reviewed. A eunuchoid 25-yr-old patient with male sex chromatin, 46 XY genotype, plasma testosterone slightly below normal, normal urinary 17-KS unaltered by gonadotropin stimulation, and bilateral absence of the testicles is presented. Examination of the inguinal canal showed a funiculus and ductus deferens residue terminating in an adipose mass. Section of the fibrous duct showed that this mass was full of capillaries and venules. Lesion between the 14th and 16th week of pregnancy is postulated.

Some experiments of nature with sex

Professor Penrose was a human geneticist but above all a human biologist interested in all aspects of man's adaptation and behaviours. However, I need not remind you of the fact that his interests were wider. They were, among others, with the field of biology itself. This interest was one reason why he was particularly delighted with some of the discoveries made on human chromosomes and their anomalies, and he shared very abundantly in the work and in the excitement of these discoveries.

Origin of 48,XXXY: the evidence of the Xg blood groups

A third family is reported in which the Xg groups give information about the origin of an XXXY member: successive non-disjunction at the first and second paternal meiotic divisions is much the most likely cause. In the two previous informative families successive non-disjunction at maternal meiotic divisions was the most likely cause. An enquiry showed the average age of 29 fathers at the birth of XXXY sons to be 32-41 years.

[X-trisomy in cattle with signs of familial disposition for meiotic disturbances]

For the first time a case of X-trisomy (XXX-gonosome aberration) in a Fleckvieh-heifer is reported. Cytogenetic examination of leukocytes and tissue cultures from the skin of this animal gave in 100% of the examined cells the karyotype 2N = 61, XXX. Except for a pronounced kyphosis of the lumbar column, there were no clinical symptoms. Sex organs and sexual function showed nothing peculiar. The teratogram from the father of the XXX-heifer showed genetical connections in the etiology of kyphosis. It seems also that in the family line an inherent genetical disposition to meiotic disturbances, in the sense of non-disjunction, exist because recently a case of an XXY-gonosome abnormality with bilateral testicle hypoplasia (bovine hypogonadism) was registered in the second generation of the father’s breed.