Macroorchidism and fragile X in mentally retarded males. Clinical, cytogenetic, and some hormonal investigations in mentally retarded males, including two with the fragile site at Xq28, fra(X)(q28)

Ataxia and Hypogonadism: a Review of the Associated Genes and Syndromes

The association of hypogonadism and cerebellar ataxia was first recognized in 1908 by Gordon Holmes. Since the seminal description, several heterogeneous phenotypes have been reported, differing for age at onset, associated features, and gonadotropins levels. In the last decade, the genetic bases of these disorders are being progressively uncovered. Here, we review the diseases associating ataxia and hypogonadism and the corresponding causative genes. In the first part of this study, we focus on clinical syndromes and genes (RNF216, STUB1, PNPLA6, AARS2, SIL1, SETX) predominantly associated with ataxia and hypogonadism as cardinal features. In the second part, we mention clinical syndromes and genes (POLR3A, CLPP, ERAL1, HARS, HSD17B4, LARS2, TWNK, POLG, ATM, WFS1, PMM2, FMR1) linked to complex phenotypes that include, among other features, ataxia and hypogonadism. We propose a diagnostic algorithm for patients with ataxia and hypogonadism, and we discuss the possible common etiopathogenetic mechanisms.

Fragile X mental retardation protein is required for programmed cell death and clearance of developmentally-transient peptidergic neurons

Fragile X syndrome (FXS), caused by loss of fragile X mental retardation 1 (FMR1) gene function, is the most common heritable cause of intellectual disability and autism spectrum disorders. The FMR1 product (FMRP) is an RNA-binding protein best established to function in activity-dependent modulation of synaptic connections. In the Drosophila FXS disease model, loss of functionally-conserved dFMRP causes synaptic overgrowth and overelaboration in pigment dispersing factor (PDF) peptidergic neurons in the adult brain. Here, we identify a very different component of PDF neuron misregulation in dfmr1 mutants: the aberrant retention of normally developmentally-transient PDF tritocerebral (PDF-TRI) neurons. In wild-type animals, PDF-TRI neurons in the central brain undergo programmed cell death and complete, processive clearance within days of eclosion. In the absence of dFMRP, a defective apoptotic program leads to constitutive maintenance of these peptidergic neurons. We tested whether this apoptotic defect is circuit-specific by examining crustacean cardioactive peptide (CCAP) and bursicon circuits, which are similarly developmentally-transient and normally eliminated immediately post-eclosion. In dfmr1 null mutants, CCAP/bursicon neurons also exhibit significantly delayed clearance dynamics, but are subsequently eliminated from the nervous system, in contrast to the fully persistent PDF-TRI neurons. Thus, the requirement of dFMRP for the retention of transitory peptidergic neurons shows evident circuit specificity. The novel defect of impaired apoptosis and aberrant neuron persistence in the Drosophila FXS model suggests an entirely new level of "pruning" dysfunction may contribute to the FXS disease state.

Role for metabotropic glutamate receptor 5 (mGluR5) in the pathogenesis of fragile X syndrome

Metabotropic glutamate receptors (mGluRs) have been implicated in a diverse variety of neuronal functions. Studies reviewed here indicate that exaggerated signalling through mGluR5 can account for multiple cognitive and syndromic features of fragile X syndrome, the most common inherited form of mental retardation and autism. Since a reduction of mGluR5 signalling can reverse fragile X phenotypes, these studies provide a compelling rationale for the use of mGluR5 antagonists for the treatment of fragile X and related disorders.

A unique form of mental retardation with a distinctive phenotype maps to Xq26-q27

We report a novel X-linked mental retardation (XLMR) syndrome, with characteristic facial dysmorphic features, segregating in a large North Carolina family. Only males are affected, over four generations. Clinical findings in the seven living affected males include a moderate degree of mental retardation (MR), coarse facies, puffy eyelids, narrow palpebral fissures, prominent supraorbital ridges, a bulbous nose, a prominent lower lip, large ears, obesity, and large testicles. Cephalometric measurements suggest that the affected males have a distinctive craniofacial skeletal structure, when compared with normative measures. Obligate-carrier females are unaffected with MR, but the results of cephalometric skeletal analysis suggest craniofacial dysmorphisms intermediate between affected males and normative control individuals. Unaffected male relatives show no clinical or cephalometric resemblance to affected males. The blood-lymphocyte karyotype and the results of DNA analysis for fragile-X syndrome and of other routine investigations are normal. Linkage analysis for polymorphic DNA markers spanning the X chromosome established linkage to Xq26-q27. Maximum LOD scores were obtained at marker DXS1047 (maximum LOD score = 3.1 at recombination fraction 0). By use of haplotype analysis, we have localized the gene for this condition to an 18-cM genetic interval flanked by ATA59C05 and GATA31E08. On the basis of both the clinical phenotype and the mapping data, we were able to exclude other reported XLMR conditions. Therefore, we believe that a unique recessive XLMR syndrome with a distinctive and recognizable phenotype is represented in this family.

A family with mental retardation, variable macrocephaly and macro-orchidism, and linkage to Xq12-q21

A family with X linked inheritance of mental retardation (XLMR) is presented. There are 10 mentally retarded males and two affected females in two generations. There are four obligatory carriers, one of whom is described as "slow". Most affected males show macrocephaly and macro-orchidism, which are typical signs of the fragile X syndrome, but have been tested cytogenetically and by analysis of the FMR1 gene and do not have this syndrome. However, some normal males in the family also exhibit macro-orchidism and macrocephaly. Linkage analysis using markers derived from the X chromosome indicates that the causative gene in this family is located in the proximal long arm of the X chromosome, in the interval Xp11-q21. Maximum lod scores of 2.96 with no recombination were found at three loci in Xq13-q21: DXS1111, DXS566, and DXS986. Recombination was observed with DXS1002 (Xq21.31) and DXS991 (Xp11.2), loci separated by about 30 Mb. Although isolation of the gene in this family will be difficult because of the size of the region involved, the localisation should be helpful in investigating other similar families with XLMR, macrocephaly, and macro-orchidism not attributable to FMR1.

Macroorchidism in FMR1 knockout mice is caused by increased Sertoli cell proliferation during testicular development

The fragile X syndrome is the most frequent hereditary form of mental retardation. This X-linked disorder is, in most cases, caused by an unstable and expanding trinucleotide CGG repeat located in the 5'-untranslated region of the gene involved, the fragile X mental retardation 1 (FMR1) gene. Expansion of the CGG repeat to a length of more than 200 trinucleotides results in silencing of the FMR1 gene promoter and, thus, in an inactive gene. The clinical features of male fragile X patients include mental retardation, autistiform behavior, and characteristic facial features. In addition, macroorchidism is observed. To study the role of Sertoli cell proliferation and FSH signal transduction in the occurrence of macroorchidism in fragile X males, we made use of an animal model for the fragile X syndrome, an Fmr1 knockout mouse. The results indicate that in male Fmr1 knockout mice, the rate of Sertoli cell proliferation is increased from embryonic day 12 to 15 days postnatally. The onset and length of the period of Sertoli cell proliferation were not changed compared with those in the control males. Serum levels of FSH, FSH receptor messenger RNA expression, and short term effects of FSH on Sertoli cell function, as measured by down-regulation of FSH receptor messenger RNA, were not changed. We conclude that macroorchidism in Fmr1 knockout male mice is caused by an increased rate of Sertoli cell proliferation. This increase does not appear to be the result of a major change in FSH signal transduction in Fmr1 knockout mice.

Endocrine and spermatological characteristics of 135 patients with bilateral megalotestis

Little is known about the biological and clinical significance of bilaterally enlarged testes (bilateral megalotestes or macroorchidism). We have investigated clinical, endocrine and spermatological characteristics of 135 andrological patients with a testicular volume of more than 25 ml bilaterally. 135 patients with normal testicular volumes served as controls. Subjects with bilateral megalotestis had higher sperm counts and better sperm morphology and motility than the controls. Levels of LH, FSH, prolactin, testosterone and estradiol were lower in the megalotestis group. This was statistically significant for LH and FSH. No testicular tumours were diagnosed in either group. We conclude that in most andrological patients with bilateral megalotestes fertility parameters are excellent despite the unusually low hormone levels found in a significant minority. No specific pathology underlying the large gonadal volume could be identified.

Fragile X (Martin-Bell) syndrome

Fragile X syndrome is a common condition resulting from a cytogenetic abnormality in the X chromosome. Mental retardation, characteristic facies, and large testes are some of the most important characteristics of the condition. The relatively high incidence of the syndrome--approximately one per thousand--the high incidence of cardiac anomalies in these individuals, the oral and facial features associated with the condition, and the paucity of reported cases in the dental literature make it particularly interesting to dentistry. Here we report the case of a 12-year-old male, including the cytogenetic and cephalometric analyses, presenting with some of the classic features and some features not commonly reported.

Macro-orchidism: light and electron microscopic study of four cases

A hormonal and quantitative light microscopy study of one man with macro-orchidism associated with mental retardation and fragile X chromosome (case no. 1) and three men with idiopathic macro-orchidism (cases no. 2 to 4) is reported. Hormonal study revealed slightly increased follicle-stimulating hormone serum levels in cases no. 1 to 3. The testes from cases no. 1 (orchidoepididymoectomy specimen) and 2 (testicular biopsy) presented interstitial edema and three different tubular patterns that were arranged in a mosaic-like manner. Type I tubules had an increased diameter (less than 220 microns), dilated lumen, and thin seminiferous epithelium usually consisting of Sertoli cells, spermatogonia, primary spermatocytes, and sometimes a few spermatids. Type II tubules had a normal diameter (180 to 220 microns) and germ cell development varied between complete spermatogenesis and Sertoli-cell-only tubules. Type III tubules had decreased diameter (less than 180 microns), atrophic seminiferous epithelium, and thickened tunica propria. The appearance of the nuclei of the Sertoli cells in the three types of tubules could be either mature or immature. Some of the mature Sertoli cells presented a granular cytoplasm. A few of these granular cells grouped together, forming nests that protruded into the tubular lumen. The testicular biopsies from cases no. 3 and 4 only presented type II tubules that contained both mature and immature Sertoli cells. Quantitative study revealed that the large testicular size was principally due to an increased tubular length in all four cases. Although the seminiferous tubule lesions and interstitial edema suggest an obstructive process, the testicular excretory ducts (studied in case no. 1) appeared normal or only slightly dilated. It is possible that the seminiferous tubule lesions (dilated lumen and germ cell depletion) might be secondary to the Sertoli cell lesions (granular cytoplasm and nuclear immature-like pattern.

The fragile-X syndrome. On the way to a behavioural phenotype

The fragile-X syndrome accounts for up to 10% of individuals with mental handicap, and 50% of cases of X-linked mental retardation. Knowledge of the genetic basis of mental functioning, psychopathology, and neuropsychology is being furthered by this recently recognised condition. The disorder has considerable significance for psychiatrists, particularly, but by no means exclusively, those working in the field of mental handicap and with children. This review outlines the slow clarification of this complex and important behavioural phenotype and the implications of these advances for identification, diagnosis, genetic counselling and a wide range of management interventions.

Fragile X screening program in New York State

Most fragile X [fra(X)] males in New York State have not been identified. Hence, a large number of female relatives are unaware of their risks for having an affected child. A program was established in New York State in 1987 to screen for the fra(X) syndrome in mentally retarded males with living relatives. The goal of the program is to identify affected males and inform their families about the diagnosis. In this way relatives would be able to assess their risks for having a fra(X) male. In order to identify the males a screening form was developed to assess 10 features which included physical characteristics, behavior, and family history. Males who exhibited at least 5 of these manifestations were selected for cytogenetic analysis. Any male who had macroorchidism or a family history of mental retardation was also included. A total of 995 males have been screened of which 352 (35%) were selected for cytogenetic analyses. Seventeen (10.5%) of the 161 completed studies were positive for fra(X). A large number of possible female carriers were identified in the families of the propositi. This program identifies fra(X) males in a population of the mentally retarded for whom there had been no previous diagnosis. By using a two-step procedure, it is possible to screen a large population of the mentally retarded for fra(X) without testing each male cytogenetically.

Fragile X checklist

A 13-item checklist that combines physical and behavioral traits typical of fragile X [fra(X)] syndrome was evaluated prospectively in the screening of 107 males with mental retardation or severe learning disabilities. The checklist was completed before we obtained cytogenetic results. Fifteen males were fra(X)-positive and the manifestations that differentiated fra(X)-positive and fra(X)-negative patients included perseverative speech, large or prominent ears, large testicles, and tactile defensiveness. The combination of physical and behavioral traits is helpful in suggesting the diagnosis and identifying high-risk patients. A total score of 16 or higher had a significant yield of fra(X)-positive patients (greater than or equal to 45%).

Fragile X frequency in a mentally retarded population in Brazil

Seventy-five male and 50 female students from 2 special schools for mildly, moderately retarded, or borderline individuals were screened clinically and cytogenetically in order to estimate the contribution of fragile X [fra(X)] syndrome to the cause of mental retardation in Brazil. We found 6 males (8%) from 4 families and 2 unrelated females (4%) with fra(X) chromosomes. One male and one female were isolated cases. The estimated frequency of Martin-Bell [fra(X)] syndrome among mentally impaired individuals in Brazil was similar to that previously reported in other countries.

The predictive value of dermatoglyphic anomalies in the diagnosis of fra(X)-positive Martin-Bell syndrome (MBS)

In a representative group of 160 institutionalized mentally retarded males without Down syndrome, prospective dermatoglyphic-cytogenetic studies were performed in order to assess the utility of the dermatoglyphic index system of Rodewald [1986] for an efficient ascertainment of patients with Martin-Bell syndrome (MBS). A negative (abnormal) score was found in 32 men (20 +/- 3%), 14 of whom (predictive value: 44 +/- 9%) were fra(X)-positive. This prevalence of 14/160 = 9 +/- 2% patients with fra(X)-positive MBS indicates that in our study most, if not all, MBS patients have been detected by the simple pre-screening of dermatoglyphics. In the MBS patients, there was no correlation between the dermatoglyphic scores and percentage of fra(X)-positive cells.

Prevalence of the fragile X syndrome in an institution for the mentally handicapped

In an investigation to find the prevalence of the fragile X (Martin Bell) syndrome in a mental handicap hospital, chromosomal investigations were carried out in 196 males selected out of a total of 512, and also in 20 female patients who were related to some of the selected males. Fragile X cells were found in 41 of the males and two of the females; in 21 of the males it was associated with macro-orchidism. The overall prevalence in the hospital for males (8.0%) ranks this syndrome next in importance to Down's syndrome as a known cause for mental handicap.

Neurofibromatosis and fragile-X syndrome in the same patient

We report on an 11 1/2-year-old boy with neurofibromatosis and the fragile-X syndrome. Clinical manifestation of neurofibromatosis include multiple cafe-au-lait spots, axillary freckles, congenital glaucoma, relative macrocephaly, radiologic findings of overtubulation of the long bones, and precocious puberty. The fragile-X syndrome manifests itself as mental retardation with behavior problems, macro-orchidism, and specific cytogenetic findings. The boy has normal serum hormone levels, but a greatly elevated FSH on a first morning void, which contains the nocturnally secreted gonadotropins. This seems to be the first reported occurrence of the fragile-X syndrome with another inherited disease.

The fragile X syndrome: the patients and their chromosomes

We have reviewed recent publications, mostly from 1980 onwards, concerned with the problem of identifying patients with the fragile X chromosome and mental retardation, considering the two practical sides of the problem, that is, identification by their external appearance and by chromosomal studies. We conclude that this condition covers a large range of physical findings which occur in varying degrees in people with the chromosome marker. We have tried to clarify the existent criteria that have to be considered for an accurate cytogenetic diagnosis.

Fragile X demonstrated retrospectively in amniotic cells cultured in low folate medium

Chromosome analysis in a boy aged 10 months, with psychomotor retardation, revealed the fragile X-chromosome in lymphocytes and skin fibroblasts cultured in low folate medium (TC 199). Amniocentesis and chromosomal analysis had been carried out during pregnancy because of advanced maternal age. Review of the slides from amniotic fluid cells grown routinely in low folate medium showed the marker X in 10.6 per cent of the metaphases. Possible explanations for the appearance of the marker X in amniotic cell culture are discussed.

Diagnosis of the fragile X syndrome (Martin-Bell syndrome). Clinical findings in 27 males with the fragile site at Xq28

The results of a clinical investigation of 27 males with the fragile X are reported; the age range was from 1 to 77 years. The medical history in pre-, peri- and early post-natal life was unremarkable. Birth weights tended to be above average. In infancy hypotonia and a large head were often found, together with retarded development. Macroorchidism was almost uniformly found after puberty, but apparently not often before. The facial features in the grown-up males were characteristic, confirming previous reports. Minor abnormalities of feet and hands were seen. Mental retardation was often in the moderate range, but all degrees were seen. Psychiatric symptoms were frequently seen, and one child was diagnosed as autistic. A developmental profile is outlined.

Carrier detection and X-inactivation studies in the fragile X syndrome. Cytogenetic studies in 63 obligate and potential carriers of the fragile X

Cytogenetic investigations by three different lymphocyte culture methods in 63 obligate and potential carriers of the fragile X [fra(X)] are reported. A difference was observed between normal and retarded carriers in the manifestation of the fra(X). An inverse relationship between percentage positive cells and age was demonstrated in normal carriers, whereas retarded carriers generally showed higher percentages at all ages. X-inactivation studies in retarded carriers compared with normal carriers showed a tendency towards a skewed inactivation pattern with an excess of early replicating fra(X) in both groups when carriers expressing high percentages of fra(X) positive cells were compared. In normal carriers with low percentage expression the tendency was apparently reversed. The relationship between the replication pattern of the fragile X and the mental status of the individual is more complicated than suggested by previous studies.

Screening of mentally retarded males for macro-orchidism and the fragile X chromosome

Four hundred forty-four male residents of a state mental retardation institution were screened for macro-orchidism. Twenty-six white males (8.3%) and two black males (1.5%) had marked macro-orchidism (greater than 34 ml). Seven of 17 whites tested for the fragile X were positive; the one black tested was negative. Thus, a minimum of 7/26 or 27% (whites) are fragile X positive indicating potential population variability, also evident from previous reports. Concurrent testing of institutionalized brother pairs indicated over half of the fragile X-positive males had a strong family history consistent with X-linked mental retardation.

Screening for fra(X)(q) in a population of mentally retarded males

Among 242 institutionalized mentally retarded males in Northern Germany screened for fra(X)(q), 15 (6.2%) with severe mental retardation expressing fra(X)(q) were detected. One patient displayed Klinefelter's syndrome in addition. All fra(X)(q) males showed the typical facial signs, but three of the adults did not express macroorchidism. A preliminary estimation of an overall frequency of 1:2000 males for the fra(X)(q) condition is suggested.