Contiguous gene syndromes due to deletions in the distal short arm of the human X chromosome

SHOX mutations in dyschondrosteosis (Leri-Weill syndrome)

Dyschondrosteosis (DCS) is an autosomal dominant form of mesomelic dysplasia with deformity of the forearm (Madelung deformity; ref. 3). Based on the observation of XY translocations (p22,q12; refs 4-6) in DCS patients, we tested the pseudoautosomal region in eight families with DCS and showed linkage of the DCS gene to a microsatellite DNA marker at the DXYS233 locus (Zmax=6.26 at theta=0). The short stature homeobox-containing gene (SHOX), involved in idiopathic growth retardation and possibly Turner short stature, maps to this region and was therefore regarded as a strong candidate gene in DCS. Here, we report large-scale deletions (in seven families) and a nonsense mutation (in one family) of SHOX in patients with DCS and show that Langer mesomelic dwarfism results from homozygous mutations at the DCS locus.

A recurrent missense mutation in the KAL gene in patients with X-linked Kallmann's syndrome

Kallmann's syndrome (KS) is defined by the association of hypogonadotropic hypogonadism and anosmia or hyposmia. Segregation analysis in familial cases has demonstrated diverse inheritance patterns, suggesting the existence of several genes regulating GnRH secretion. Genetic defects have been demonstrated in the KAL gene, located on the Xp22.3 region, explaining the X-linked form of the disease. We report molecular findings regarding the KAL gene in 12 unrelated males with X-linked KS. PCR of the 14 exons of the KAL gene was performed on genomic DNA. PCR products of all exons were purified and sequenced. Genetic defects in the KAL gene were found in 7 patients. One exhibits a deletion from exon 3 to exon 5. Six individuals present a previously unidentified missense mutation in exon 11, consisting of a G to A substitution at codon 514 (GAA to AAA). In the remaining 5 individuals, no mutations were observed. We also found three different polymorphic changes. The first one, in exon 2, had not been reported previously. The other two were located at exons 11 and 12. The deletion described, comprises only part (exon 5) of the coding region of the first fibronectin type III-like repeat of the KAL protein. The rest of the deletion comprises part of the conserved cysteine-rich N-terminal region that corresponds to the whey acidic protein motif. The same missense mutation was found in 6 of the 12 patients, indicating the possibility that it derived from a common ancestor or suggesting the presence of a hot spot in this region of the gene.

Modulation of serum testosterone and autonomic function through stimulation of the male human vomeronasal organ (VNO) with pregna-4,20-diene-3,6-dione

In mammals, external chemosensory signals from conspecifics of the opposite sex acting on vomeronasal organ receptors can modulate the release of gonadotropins. There is developmental, anatomical and functional evidence showing that the human vomeronasal organ (VNO) has the characteristics of a chemosensory organ. We have been using naturally occurring human pheromones to serve as models for designing novel synthetic compounds that we call vomeropherins. In previous publications we reported that vomeropherin pregna-4,20-diene-3,6-dione (PDD) delivered to the VNO of normal female and male human volunteers significantly affected male subjects only, decreasing respiration and cardiac frequency, augmenting alpha brain waves, and significantly decreasing serum luteinizing hormone (LH) and follicle stimulating hormone (FSH). Results of the present work confirm that PDD produces a local dose-dependent effect in the male human VNO. This is followed by a mild parasympathomimetic effect characterized by 10% increase of vagal tone, together with decreased frequency of electrodermal activity events. Furthermore, PDD locally delivered to the male human VNO significantly decreases serum LH and testosterone (p < 0.01). The present results contribute additional evidence supporting the functionality of the human VNO and its repercussions in autonomic and psychophysiological functions, as well as in neuroendocrine secretions.

Summary of ocular genetic disorders and inherited systemic conditions with eye findings

Of the close to 10,000 known inherited disorders that affect humankind, a disproportionately high number affect the eye. The total number of genes responsible for the normal structure, function, and differentiation of the eye is unknown, but the list of these genes is rapidly and constantly growing. The objective of this paper is to provide a current list of mapped and/or cloned human eye genes that are responsible for inherited diseases of the eye. The ophthalmologist should be aware of recent advances in molecular technology which have resulted in significant progress towards the identification of these genes. The implications of this new knowledge will be discussed herein.

Immunoreactive gonadotropin-releasing hormone (GnRH) is detected only in the form of chicken GnRH-II within the brain of the green anole, Anolis carolinensis

The presence of multiple forms of gonadotropin-releasing hormone (GnRH) within a single brain is common among vertebrate species. In previous studies of reptiles, two forms of GnRH were isolated from the brain of alligators and the primary structure was determined to be that of chicken (c)GnRH-I and cGnRH-II. GnRH has also been detected by indirect methods in other reptiles including turtles, lizards, and snakes. We used a combination of high-performance liquid chromatography (HPLC) and radioimmunoassay to determine the number and molecular form(s) of GnRH in the brain of a lizard, Anolis carolinensis, that was reported to lack GnRH cells in the forebrain. Immunoreactivity was detected in the same HPLC elution position in which synthetic cGnRH-II elutes, but not in any other position. Detection was based on five antisera that among them detect the 12 known forms of GnRH; these antisera include ones that are specific to cGnRH-I and cGnRH-II. We conclude that the lizard A. carolinensis contains cGnRH-II, but not cGnRH-I or another known form of GnRH. These data, coupled with our earlier immunocytochemical study, suggest that the lizard studied here lacks cGnRH-I, the form that is found in the terminal nerve, olfactory bulb, and forebrain in nonsquamate reptiles and in birds. Our hypothesis is that the presence of both cGnRH-I and cGnRH-II in the brain is ancestral in the reptilian lineage and retained in the orders that include turtles (Chelonia) or alligators (Crocodilia). However, the pattern in the order Squamata varies: in A. carolinensis, only cGnRH-II is present in the brain and cGnRH-I is absent, whereas in the snake Thamnophilis sirtalis, cGnRH-I is retained and cGnRH-II is absent in the brain, as recently reported. This raises the question of how reproduction is controlled in reptiles that lack one form of GnRH.

Del (X)(p21.2) in a mother and two daughters with variable ovarian function

We report a family in which a woman with the mosaic karyotype 45,X/46,X,del(X)(p21.2) transmitted the deleted X chromosome to two daughters. The nature of the deletion was confirmed by fluorescent in situ hybridization (FISH). All three family members showed somatic Ullrich-Turner syndrome features, but only one daughter had ovarian failure. These observations have implications for the diagnosis of Ullrich-Turner syndrome and genotype/phenotype correlations of X chromosome deletions.

Craniofacial morphology in patients with Kallmann's syndrome with and without cleft lip and palate

OBJECTIVE

Kallmann's syndrome is characterized by the association of hypogonadotropic hypogonadism and anosmia or hyposmia. The principal endocrine defect of hypogonadotropic hypogonadism is a failure to secrete luteinizing hormone-releasing hormone (LHRH), resulting in underdevelopment of the pituitary gonadotropes and an inability to synthesize and release luteinizing hormone and follicle-stimulating hormone. The purpose of the present investigation was to describe the dentition and the craniofacial morphology in patients diagnosed with Kallmann's syndrome.

DESIGN

The sample consisted of 11 patients, 2 of whom also had bilateral cleft lip and palate. Radiographic investigations, including cephalometry, were performed. Comparisons were made to normal individuals and to cleft lip individuals without Kallmann's syndrome.

RESULTS

Dentition: tooth agenesis occurred more frequently in patients with Kallmann's syndrome. Craniofacial morphology: Increased mandibular inclination and mandibular angulation were seen in Kallmann patients. When clefting also occurred, extreme retrognathism of both maxilla and mandible was seen, a deviation which seemingly worsened during growth. The anterior cranial base and the sphenoid bone showed an altered morphology in one of the patients with Kallman's syndrome.

CONCLUSIONS

An early diagnosis of Kallmann's syndrome is very important because the prognosis for endocrine treatment thereby improves, and therefore, it is recommended that the sense of smell be evaluated in patients with the craniofacial morphology described.

Pseudoautosomal deletions encompassing a novel homeobox gene cause growth failure in idiopathic short stature and Turner syndrome

Growth retardation resulting in short stature is a major concern for parents and due to its great variety of causes, a complex diagnostic challenge for clinicians. A major locus involved in linear growth has been implicated within the pseudoautosomal region (PAR1) of the human sex chromosomes. We have determined an interval of 170 kb of DNA within PAR1 which was deleted in 36 individuals with short stature and different rearrangements on Xp22 or Yp11.3. This deletion was not detected in any of the relatives with normal stature or in a further 30 individuals with rearrangements on Xp22 or Yp11.3 with normal height. We have isolated a homeobox-containing gene (SHOX) from this region, which has at least two alternatively spliced forms, encoding proteins with different patterns of expression. We also identified one functionally significant SHOX mutation by screening 91 individuals with idiopathic short stature. Our data suggest an involvement of SHOX in idiopathic growth retardation and in the short stature phenotype of Turner syndrome patients.

Mental retardation in a boy with an interstitial deletion at Xp22.3 involving STS, KAL1, and OA1: implication for the MRX locus

Although genotype-phenotype correlations in male patients with various types of nullisomy for Xp22.3 have assigned a locus for X-linked mental retardation (MRX) to an approximately 3-Mb region between DXS31 and STS, the precise location has not been determined. In this paper, we describe a 14 7/12 year old Japanese boy with mental retardation and an interstitial deletion at Xp22.3 involving STS, KAL1, and OA1, and compare the deletion map with that of previously reported three familial male patients with low-normal intelligence and a similar interstitial deletion at Xp22.3. The results suggest that the MRX gene is further localized to the roughly 1.5-Mb region between DXS1060 and DXS1139.

Regional localisation of two non-specific X-linked mental retardation genes (MRX30 and MRX31)

Two genes responsible for X-linked mental retardation have been localised by linkage analysis. MRX30 maps to a 28 cM region flanked by the loci DXS990 (Xq21.3) and DXS424 (Xq24). A significant multipoint lod score of 2.78 was detected between the loci DXS1120 and DXS456. MRX31 maps to a 12 cM region that spans the centromere from DXS1126 (Xp11.23) to DXS1124 (Xq13.3). Significant two-point lod scores, at a recombination fraction of zero, were obtained with the loci DXS991 (Zmax = 2.06), AR (Zmax = 3.44), PGK1P1 (Zmax = 2.06) and DXS453 (Zmax = 3.31). The MRX30 localisation overlaps that of MRX8, 13, 20 and 26 and defines the position of a new MRX gene on the basis of a set of non-overlapping regional localisations. The MRX31 localisation overlaps the localisations of many of the pericentromeric MRX loci (MRX 1, 4, 5, 7, 8, 9, 12, 13, 14, 15, 17, 20, 22 and 26). There are now at least 8 distinct loci associated with non-specific mental retardation on the X chromosome defined, in order from pter to qter, by localisation for MRX24, MRX2, MRX10, MRX1, MRX30, MRX27, FRAXE and MRX3.

An analysis of Xq deletions

We characterized by fluorescence in situ hybridization and Southern blotting 14 partial Xq monosomies, 11 due to terminal deletions and 3 secondary to X/autosome translocations. Three cases were mosaics with a XO cell line. In view of the possible role played by telomeres in chromosome segregation, we hypothesize a relationship between the loss of telomeric sequences in terminal deletions and the presence of 45,X cells. A correlation between phenotype and extent of deletion reveal that there is no correspondence between the size of the deletion and impairment of gonadal function. Turner stigmata are absent in patients without an XO cell line, when the breakpoint is distal to Xq24. A low birthweight is present whenever the breakpoint is at q22 or more proximal.

Ullrich-Turner syndrome is not caused by haploinsufficiency of RPS4X

Ullrich-Turner syndrome (UTS) is frequently associated with monosomy X but may also occur with structural aberrations of the X and the Y chromosomes. It has been hypothesized that the ribosomal protein genes RPS4X and RPS4Y play a critical role in the prevention of UTS. Individual patients with a 46,X,i(Xq) karyotype cannot be differentiated phenotypically from 45,X UTS patients and carry three gene copies of RPS4X. Since haploinsufficiency of one or several gene(s) is thought to cause the UTS phenotype, direct assessment of RPS4X expression levels in these patients should establish whether RPS4X is involved in UTS. We have investigated fibroblasts of four 46,X,i(Xq) UTS patients with typical symptoms and a non-mosaic chromosome complement, and have found significantly increased RPS4X mRNA levels in all patients. Based on our results, we conclude that haploinsufficiency of RPS4X is not the cause of UTS.

Refinement of the locus for X-linked recessive chondrodysplasia punctata

Although the locus for X-linked recessive chondrodysplasia punctata (CDPX1) has been mapped to the region between PABX and DXS31 (the critical region is about 3 Mb long), the precise location within the critical region has not been determined. In this paper, we describe a boy with a 46,Y,der(X)t(X;Y)(p22.3;q11)mat karyotype and review the genotype-phenotype correlations in three male patients with the combination of apparent lack of clinical features of CDPX1 and a partial deletion of the critical region. The results suggest that the region defined by the two BssHII sites at 3180 and 3570 kb from the Xp telomere may be the target region for the CDPX1 locus.

Association between X-linked hypophosphatemic rickets and Klinefelter's syndrome: effects on growth and body proportion

Growth failure with disproportionate short stature is the major clinical feature of patients with X-linked hypophosphatemic rickets (HYP). We studied the pattern of linear growth and body proportion in an untreated normally growing HYP child also affected by Klinefelter's syndrome. Auxologic data were compared with those of a HYP half-brother who showed growth failure despite long-term treatment either with vitamin D or with vitamin-D-analog plus phosphate salt supplementation. The degree of body disproportion changed from negative values to positive values in the proband, whereas it was reduced in the half-brother. We conclude that, in the proband, the normal pattern of growth and the lack of the typical body disproportion as seen in HYP patients are attributable to the concomitant presence of Klinefelter's syndrome.

High-density physical mapping of a 3-Mb region in Xp22.3 and refined localization of the gene for X-linked recessive chondrodysplasia punctata (CDPX1)

The study of patients with chromosomal rearrangements has led to the mapping of the gene responsible for X-linked recessive chondrodysplasia punctata (CDPX1; MIM 302950) to the distal part of the Xp22.3 region, between the loci PABX and DXS31. To refine this mapping, a yeast artificial chromosome (YAC) contig map spanning this region has been constructed. Together with the YAC contig of the pseudo-autosomal region that we previously established, this map covers the terminal 6 Mb of Xp, with an average density of 1 probe every 100 kb. Newly isolated probes that detect segmental X-Y homologies on Yp and Yq suggest multiple complex rearrangements of the ancestral pseudoautosomal region during evolution. Compilation of the data obtained from the study of individuals carrying various Xp22.3 deletions led us to conclude that the CDPX disease displays incomplete penetrance and, consequently, to refine the localization of CDPX1 to a 600-kb interval immediately adjacent to the pseudoautosomal boundary. This interval, in which 12 probes are ordered, provides the starting point for the isolation of CDPX1.

Mild phenotypic effects of a de novo deletion Xpter-->Xp22.3 and duplication 3pter-->3p23

We report on a girl with a de novo monosomy Xpter-->Xp22.3 and trisomy 3pter-->3p23, normal development and stature, mildly affected phenotype, and learning disabilities with a low normal level of intelligence. Late replication studies using BudR demonstrated that the entire der(X) was inactive in 30% of cells. In 62% of cells the inactivation did not spread to the autosomal segment in the der(X). The normal X was inactivated in 8% of cells. Quantitative X-inactivation studies using the human androgen receptor locus assay (HAR) on peripheral leukocytes and buccal epithelial cells showed extreme skewing of methylation (90.4% of the paternal allele). The correlation of cytogenetic and molecular data suggest that the mild phenotype of the proposita is most likely due to preferential inactivation of the entire der(X), which seems to be of paternal origin.

SRY alone can induce normal male sexual differentiation

Most individuals with the rare 46,XX male "syndrome" arise due to an unequal interchange between Xp and Yp termini during paternal meiosis. The pattern of Y-sequences in these patients varies considerably, but very few cases have been reported showing only SRY. The phenotype in these patients is also variable ranging from severe impairment of the external genitalia through hypospadias and/or cryptorchidism to occasional normal male phenotype. We report a Mexican 46,XX male patient without genital ambiguities in whom DNA analysis showed the presence of SRY and the absence of ZFY. We conclude that in this case SRY alone was enough for complete male sexual differentiation.

Development and physical analysis of YAC contigs covering 7 Mb of Xp22.3-p22.2

A total of 54 YAC clones have been isolated from the region of Xp22.2-p22.3 extending from the amelogenin gene locus to DXS31. Restriction analysis of these clones in association with STS contenting and end clone analysis has facilitated the construction of 6 contigs covering a total of 7 Mb in which 20 potential CpG islands have been located. Thirty new STSs have been developed from probe and YAC end clone sequences, and these have been used in the analysis of patients suffering from different combinations of chondrodysplasia punctata, mental retardation, X-linked ichthyosis, and Kallmann syndrome. The results suggest that (1) the gene for chondrodysplasia punctata must lie between the X chromosome pseudoautosomal boundary (PABX) and DXS1145; (2) a gene for mental retardation lies between DXS1145 and the sequence tagged site GS1; and (3) the gene for ocular albinism type 1 lies proximal to the STS G13. The CpG islands within the YAC contigs constitute valuable markers for the potential positions of genes. Genes found associated with any of these potential CpG islands would be possible candidates for the disease genes mentioned above.

A clinical and genetic study of X-linked recessive ichthyosis and contiguous gene defects

X-linked recessive ichthyosis (XLI) is caused by a deletion, or mutation, of the steroid sulphatase gene on the distal short arm of the X chromosome (Xp22.3). This region of the X chromosome is particularly susceptible to deletions. Such deletions can occasionally extend to involve neighbouring genes, causing a contiguous gene defect. Therefore, XLI may be associated with Kallmann's syndrome (KS), mental retardation, X-linked recessive chondrodysplasia punctata and short stature. We have reviewed 33 patients with XLI. Nine showed evidence of contiguous gene defects. A further four had neurological deficit sustained at the time of birth. This study highlights the importance of screening patients with X-linked recessive ichthyosis for neighbouring genetic disorders and, in particular, the early identification of KS, as delay in diagnosis may lead to infertility and osteoporosis. Parents should be warned about possible obstetric complications due to prolonged labour in future pregnancies.

Association of isolated hypogonadotropic hypogonadism, pronounced hypodontia and the Wolff-Parkinson-White syndrome

Diagnosis of idiopathic isolated hypogonadotropic hypogonadism was made in a 22-year-old female patient referred for primary amenorrhoea. It was considered a separate entity from Kallmann's syndrome, because it was not accompanied by anosmia or other specific pleiotropic features. On the other hand, the patient showed severe hypodontia and an intermittent Wolff-Parkinson-White syndrome. To our knowledge, this association has never been reported before. This unusual phenotype points to a nonrandom association. However, no information in the literature is available to consider a new single gene defect or a contiguous gene syndrome.

Regional localisation of a non-specific X-linked mental retardation gene (MRX19) to Xp22

A gene responsible for a non-specific form of X-linked mental retardation (MRX19) was localised by linkage analysis. Exclusions and regional localisation were made using 21 highly informative PCR-based markers along the X chromosome. Significant lod scores at a recombination fraction of zero were detected with the marker loci DXS207, DXS987 (Zmax = 3.58) and DXS999 (Zmax = 3.28) indicating that this gene is localised to the proximal portion of Xp22. Recombination between MRX19 and the flanking loci KAL and DXS989 was observed. The multipoint CEPH background map, with map distances in cM, is DXS996-1.8-KAL-19.0-DXS207-0.9-[DXS987,DXS443 ]-4.3-DXS999-3.5-DXS365-14.0-DXS989. Two other MRX disorders and two syndromal mental retardations, Coffin-Lowry syndrome and Partington syndrome, have been mapped to this region. There is a possibility that the 3 MRX disorders are the same entity. Most MRX disorders remain clustered around the pericentromeric region.

Linkage analysis of 62 X-chromosomal loci excludes the X chromosome in an Icelandic family showing apparent X-linked recessive inheritance of neural tube defects

We report here the findings of a linkage analysis, involving numerous markers from the human X chromosome, in an attempt to localise a putative gene causing apparent X-linked spina bifida and anencephaly (SBA) in a large Icelandic pedigree. Two-point linkage analysis was performed using markers from 62 informative loci in this family. Although small positive lod scores were found at a number of these loci, none reached the significance level for linkage. Haplotypes were extensively analysed and found to exclude linkage to the X chromosome.

Deletions of Xq and growth deficit: a review

A critical review of the literature disclosed 44 cases with a 46,X,Xq- karyotype without apparent mosaicism. Of these, 17 were of normal height (compared to the respective population), 11 had a height of over 1 SD below the mean, and 16 had a height of over 2 SD below the mean with breakpoints between Xq13 and Xq25. Since patients of normal height occurred with breakpoints as proximal as Xq13 we conclude that there is no major "growth gene" on Xq distal to q13. The most likely explanation for the variable phenotypic effect of Xq- is to assume that growth gene(s) in Xp or proximal Xq are inactivated on such a chromosome with some variability similar to the variable spreading of X inactivation seen in some X-autosome translocations.

A patient with an interstitial deletion in Xp22.3 locates the gene for X-linked recessive chondrodysplasia punctata to within a one megabase interval

A male patient carrying an interstitial deletion in Xp22.3 and affected by Kallmann syndrome, X-linked ichthyosis and mental retardation, but without chondrodysplasia punctata or short stature, was investigated with molecular probes from the distal Xp22.3 region. By means of a novel probe, M115, from the relevant region, the distal deletion breakpoint was shown to be between 3.18 and 3.57 Mb from Xptel. As the patient is not affected by X-linked recessive chondrodysplasia punctata, the gene for this disease can therefore be located to within an interval of less than one megabase proximal to the pseudoautosomal boundary. If the chondrodysplasia punctata gene is associated with a CpG island, this leaves only two islands at 2760 and 3180 kb from the Xp telomere as the most promising candidate sites for this gene.

Microphthalmia with linear skin defects (MLS) syndrome: clinical, cytogenetic, and molecular characterization

The microphthalmia with linear skin defects (MLS) syndrome (MIM 309801) is a severe developmental disorder observed in XX individuals with distal Xp segmental monosomy. The phenotype of this syndrome overlaps with that of both Aicardi (MIM 304050) and Goltz (MIM 305600) syndromes, two X-linked dominant, male-lethal disorders. Here we report the clinical, cytogenetic, and molecular characterization of 3 patients with this syndrome. Two of these patients are females with a terminal Xpter-p22.2 deletion. One of these 2 patients had an aborted fetus with anencephaly and the same chromosome abnormality. The third patient is an XX male with Xp/Yp exchange spanning the SRY gene which results in distal Xp monosomy. The extensive clinical variability observed in these patients and the results of the molecular analysis suggest that X-inactivation plays an important role in determining the phenotype of the MLS syndrome. We propose that the MLS, Aicardi, and Goltz syndromes are due to the involvement of the same gene(s), and that different patterns of X-inactivation are responsible for the phenotypic differences observed in these 3 disorders. However, we cannot rule out that each component of the MLS phenotype is caused by deletion of a different gene (a contiguous gene syndrome).

Genetic mapping of the Kallmann syndrome and X linked ocular albinism gene loci

The X linked form of Kallmann syndrome (KAL) and X linked ocular albinism (OA1) have both been mapped to Xp22.3. We have used a dinucleotide repeat polymorphism at the Kallmann locus to type 17 X linked ocular albinism families which had previously been typed for the Xg blood group (XG) and the DNA markers DXS237 (GMGX9), DXS143 (dic56), and DXS85 (782). Close linkage was found between KAL and OA1 with a maximum lod score (Zmax) of 30.14 at a recombination fraction (theta max) of 0.06 (confidence interval for theta: 0.03-0.10). KAL was also closely linked to DXS237 (Zmax = 15.32; theta max = 0.05; CI 0.02-0.12) and DXS143 (Zmax = 14.57; theta max = 0.05; CI 0.02-0.13). There was looser linkage to the Xg blood group (XG) and to DXS85 (782). Multipoint linkage analysis gave the map: Xpter-XG-0.13-DXS237-0.025-KAL-0.025-DXS143-0.01 5-OA1-0.09-DXS85-Xcen. Placement of OA1 proximal to DXS143 was supported by odds of 2300:1 compared to other orders. This confirms our previous localisation of OA1 and improves the genetic mapping of both disease loci.

Chromosomal rearrangement segregating with adrenoleukodystrophy: a molecular analysis

The relationship between X chromosome-linked adrenoleukodystrophy and the red/green color pigment gene cluster on Xq28 was investigated in a large kindred. The DNA in a hemizygous male showed altered restriction fragment sizes compatible with at least a deletion extending from the 5' end of the color pigment genes. Segregation analysis using a DNA probe within the color pigment gene cluster showed significant linkage with adrenoleukodystrophy (logarithm of odds score of 3.19 at theta = 0.0). These data demonstrate linkage, rather than association, between a unique molecular rearrangement in the color pigment gene cluster and adrenoleukodystrophy. The DNA changes in this region are thus likely to be helpful for determining the location and identity of the responsible gene.

Molecular analysis of a ring chromosome X in a family with fragile X syndrome

The phenotypically normal sister of a patient affected by fragile X syndrome was referred for genetic counselling and was found to carry a mosaic karyotype 46,X,r(X)/45,X. Because the probability of the simultaneous chance occurrence of fragile X syndrome and a ring chromosome X in the same family is very low, we postulated that the breakpoint of the ring chromosome X originated in the cytogenetic break in Xq27.3 responsible for fragile X syndrome. In order to determine the relative positions of the breakpoint on the ring chromosome X and the (CGG)n unstable sequence responsible for the fragile X mutation, we used molecular markers to analyse the telomeric regions of chromosome X in this family. The results showed that the ring chromosome X was the maternal fragile X chromosome and that the telomeric deletion on the long arm encompassed the (CGG)n sequence. This suggests that the cytogenetic break in Xq27.3 is distinct from the unstable (CGG)n sequence, or that the break followed by the end-to-end fusion creating the ring chromosome was not completely conservative. Analysis of DNA markers on the short arm of chromosome X evidenced a deletion of a large part of the pseudoautosomal region, allowing us to position the genes involved in stature and in some syndromes associated with telomeric deletions of Xp on the proximal side of the pseudoautosomal region.

Analysis of a terminal Xp22.3 deletion in a patient with six monogenic disorders: implications for the mapping of X linked ocular albinism

The molecular characterisation of chromosomal aberrations in Xp22.3 has established the map position of several genes with mutations resulting in diverse phenotypes such as short stature (SS), chondrodysplasia punctata (CDPX), mental retardation (MRX), ichthyosis (XLI), and Kallmann syndrome (KAL). We describe the clinical symptoms of a patient with a complex syndrome compatible with all these conditions plus ocular albinism (OA1). He has a terminal Xp deletion of at least 10 Mb of DNA. Both the mother and sister of the patient are carriers of the deletion and show a number of traits seen in Turner's syndrome. The diagnosis of ocular albinism was confirmed in the patient and his mother, who shows iris translucency, patches and streaks of hypopigmentation in the fundus, and macromelanosomes in epidermal melanocytes. By comparative deletion mapping we can define a deletion interval, which locates the OA1 gene proximal to DXS143 and distal to DXS85, with the breakpoints providing valuable starting points for cloning strategies.

The pseudoautosomal regions of the human sex chromosomes

In human females, both X chromosomes are equivalent in size and genetic content, and pairing and recombination can theoretically occur anywhere along their entire length. In human males, however, only small regions of sequence identity exist between the sex chromosomes. Recombination and genetic exchange is restricted to these regions of identity, which cover 2.6 and 0.4 Mbp, respectively, and are located at the tips of the short and the long arm of the X and Y chromosome. The unique biology of these regions has attracted considerable interest, and complete long-range restriction maps as well as comprehensive physical maps of overlapping YAC clones are already available. A dense genetic linkage map has disclosed a high rate of recombination at the short arm telomere. A consequence of the obligatory recombination within the pseudoautosomal region is that genes show only partial sex linkage. Pseudoautosomal genes are also predicted to escape X-inactivation, thus guaranteeing an equal dosage of expressed sequences between the X and Y chromosomes. Gene pairs that are active on the X and Y chromosomes are suggested as candidates for the phenotypes seen in numerical X chromosome disorders, such as Klinefelter's (47,XXY) and Turner's syndrome (45,X). Several new genes have been assigned to the Xp/Yp pseudoautosomal region. Potential associations with clinical disorders such as short stature, one of the Turner features, and psychiatric diseases are discussed. Genes in the Xq/Yq pseudoautosomal region have not been identified to date.

A high resolution deletion map of human chromosome Xp22

We have developed a 32-interval deletion panel for human chromosome Xp22 spanning about 30 megabases of genomic DNA. DNA samples from 50 patients with chromosomal rearrangements involving Xp22 were tested with 60 markers using a polymerase chain reaction strategy. The ensuing deletion map allowed us to confirm and refine the order of previously isolated and newly developed markers. Our mapping panel will provide the framework for mapping new sequences, for orienting chromosome walks in the region and for projects aimed at isolating genes responsible for diseases mapping to Xp22.

Functional equivalence of human X- and Y-encoded isoforms of ribosomal protein S4 consistent with a role in Turner syndrome

Several genes are found on both the human X and Y chromosomes in regions that do not recombine during male meiosis. In each case, nucleotide sequence analysis suggests that these X-Y gene pairs encode similar but nonidentical proteins. Here we show that the human Y- and X-encoded ribosomal proteins, RPS4Y and RPS4X, are interchangeable and provide an essential function: either protein rescued a mutant hamster cell line that was otherwise incapable of growth at modestly elevated temperatures. These findings are consistent with the hypothesis that RPS4 deficiency has a role in Turner syndrome, a complex human phenotype associated with monosomy X.

Prenatal in situ hybridization test for deleted steroid sulfatase gene

X-linked ichthyosis results from steroid sulfatase (STS) deficiency; 90% of affected patients have a complete deletion of the entire 146 kb STS gene on the distal X chromosome short arm (Xp22.3). In these families prenatal diagnosis and carrier testing can be completed in 2 days by hybridizing simultaneously 2 different cosmid probes labeled with fluorescein or Texas red and counterstaining interphase nuclear DNA with DAPI. An STS gene probe labeled with Texas red hybridizes specifically to the steroid sulfatase gene on the X chromosome. A second flanking probe labeled with fluorescein hybridizes to both the normal Y chromosome and normal and STS deleted X chromosomes. In this fashion the interphase nuclei of normal males, affected males, normal females, and carrier females can be distinguished unambiguously. Because normal males and carrier females each show two yellow-green fluorescein spots and one Texas red STS spot, use of this test prenatally requires determining fetal sex independently with repetitive X and Y chromosome-specific probes. This procedure can be used with lymphocytes, direct and cultured chorionic villus cells, direct and cultured amniocytes, and fibroblasts. Similar methods are anticipated to be useful for rapid diagnostic assessment of other aneuploid gene disorders.

Sex chromosome aberrations and stature: deduction of the principal factors involved in the determination of adult height

Although sex chromosome aberrations are frequently associated with statural changes, the underlying factors have not been clarified. To define the factors leading to the statural changes, we took the following three steps: (1) determination of the mean adult height in nonmosaic Caucasian patients with sex chromosome aberrations reported in the literature (assessment of genetic height potential); (2) assessment of the validity of factors that could influence stature; and (3) correlation of the mean adult height with the effects of specific growth-related factors. The results indicate that the adult height in patients with sex chromosome aberrations may primarily be defined by the dosage effect of pseudoautosomal and Y-specific growth genes, together with the degree of growth disadvantage caused by alteration of the quantity of euchromatic or non-inactivated region.

Functional disomy of Xp22-pter in three males carrying a portion of Xp translocated to Yq

A number of Xp22;Yq11 translocations involving the transposition of Yq material to the distal short arm of the X chromosome have been described. The reciprocal product, i.e. the derivative Y chromosome resulting from the translocation of a portion of Xp to Yq, has never been recovered. We searched for this reciprocal product by performing dosage analysis of Xp22-pter loci in 9 individuals carrying a non-fluorescent Y chromosome. In three mentally retarded and dysmorphic patients, dosage analysis indicated the duplication of Xp22 loci. Use of the highly polymorphic probe CRI-S232 demonstrated the inheritance of paternal Xp-specific alleles in the probands. In situ hybridization, performed in one case, confirmed that 29CL pseudoautosomal sequences were present, in addition to Xpter and Ypter, in the telomeric portion of Yq. To our knowledge, these are the first cases in which the translocation of Xp material to Yq has been demonstrated. The X and Y breakpoints were mapped in the three patients by dosage and deletion analysis. The X breakpoint falls, in the three cases, in a region of Xp22 that is not recognized as sharing sequence similarities with the Y chromosome, thus suggesting that these translocations are not the result of a homologous recombination event.

Deletion analysis maps ocular albinism proximal to the steroid sulphatase locus

We describe a pedigree in which four male members are affected by a contiguous gene abnormality involving the short arm of the X chromosome (Xp22.32). Bivariate flow cytometry of lymphoblastoid cell lines from two of these individuals and a normal male showed a 6-7 megabase deletion in affected males, and high resolution chromosomal G-banding of an obligate heterozygote showed the deletion to reside in the Xp22.32 region. Affected members had X-linked ichthyosis due to steroid sulphatase deficiency, Kallmann's syndrome, but no ocular albinism. In two out of four affected individuals studied, there was unilateral renal agenesis. Deletion analysis using the Xp22.32 markers MIC2, DXS31, DXS 89, GMGX9, DXS278, DXS143, and DXS9 showed that the deletion extended from DXS31 to DXS143 (inclusive). The absence of ocular albinism in this pedigree shows conclusively that the X-linked ocular albinism gene resides proximal to the DXS143 locus. Further, the inconstant association of unilateral renal agenesis with X-linked Kallmann's syndrome, even when the latter is caused by a complete deletion of the gene, suggests that the absence of the X-linked Kallmann gene can be compensated in renal development.

Absent chondrodysplasia punctata in a male with an Xp terminal deletion involving the putative region for CDPX1 locus

This is a follow-up report on a male patient with a 46,Y,r(X) karyotype. Although he had no clinico-radiological features of X-linked recessive chondrodysplasia punctata (CDPX1), molecular studies revealed an Xp terminal deletion involving the putative region for the CDPX1 locus (PABX-DXS31). We suspect that the absence of CDPX1 may be attributable to the nature of the disease and the extreme short stature of the patient (mean -5.6 S.D.).

The human Y chromosome: a 43-interval map based on naturally occurring deletions

A deletion map of the human Y chromosome was constructed by testing 96 individuals with partial Y chromosomes for the presence or absence of many DNA loci. The individuals studied included XX males, XY females, and persons in whom chromosome banding had revealed translocated, deleted, isodicentric, or ring Y chromosomes. Most of the 132 Y chromosomal loci mapped were sequence-tagged sites, detected by means of the polymerase chain reaction. These studies resolved the euchromatic region (short arm, centromere, and proximal long arm) of the Y chromosome into 43 ordered intervals, all defined by naturally occurring chromosomal breakpoints and averaging less than 800 kilobases in length. This deletion map should be useful in identifying Y chromosomal genes, in exploring the origin of chromosomal disorders, and in tracing the evolution of the Y chromosome.

Xp22.3 microdeletion syndrome with microphthalmia, sclerocornea, linear skin defects, and congenital heart defects

We report on an infant girl with congenital erythematous, linear skin lesions on face and neck, bilateral microphthalmia, sclerocornea, cataracts, and a complex cardiac anomaly including atrial septal and ventricular septal defects. This patient had an Xp22.3 microdeletion and a chromosome satellite on the abnormal X p-arm. The abnormal X chromosome was late replicating in peripheral blood lymphocytes and cultured skin fibroblasts. Four other patients with similar congenital anomalies and Xp deficiency have been reported previously and are compared with this patient. One patient had an interstitial or terminal deletion, but in others the material translocated to Xp22.3 was variable (Yq material in two patients, and Yp material and an unidentifiable satellite in one patient each). Several mechanisms are suggested by which this chromosome abnormality might produce this phenotype in these patients. Our patient is the first with this syndrome to have a congenital heart defect.

Chromosomal localisation of a pseudoautosomal growth gene(s)

Although recent molecular studies in patients with sex chromosome aberrations are consistent with a growth gene(s) being present in the pseudoautosomal region (PAR), the precise location has not been determined. In this report, we describe a Japanese boy and his mother with an interstitial deletion in Xp22.3 and review the correlation between genotype and stature in six cases of partial monosomy of the PAR. The results indicate that the region from DXYS20 to DXYS15 is the critical region for the putative growth gene(s).

Kallmann syndrome due to a translocation resulting in an X/Y fusion gene

The X-linked Kallmann syndrome gene was recently cloned and homologous sequences of unknown functional significance identified on the Y chromosome. We now describe a patient with Kallmann syndrome carrying an X;Y translocation resulting from abnormal pairing and precise recombination between the X-linked Kallmann syndrome gene and its homologue on the Y. The translocation created a recombinant, non-functional Kallmann syndrome gene identical to the normal X-linked gene with the exception of the 3' end which is derived from the Y. Our findings indicate that the 3' portion of the Kallmann syndrome gene is essential for its function and cannot be substituted by the Y-derived homologous region, although a 'position' effect remains a formal possibility.

Comparison of adult height between patients with XX and XY gonadal dysgenesis: support for a Y specific growth gene(s)

Adult height was compared between published cases of patients with XX gonadal dysgenesis (XXGD) and those with XY gonadal dysgenesis (XYGD). The mean adult height of XYGD patients (171.0 cm (SD 7.8), n = 27) was significantly greater than that of XXGD patients (164.4 cm (7.7), n = 27) (p less than 0.01). This finding supports the existence of a Y specific growth gene(s) which promotes statural growth independently of the effects of gonadal sex steroids.

Chondrodysplasia punctata: a boy with X-linked recessive chondrodysplasia punctata due to an inherited X-Y translocation with a current classification of these disorders

Chondrodysplasia punctata (CDP) is a heterogeneous group of rare bone dysplasias characterized by punctate calcification of cartilage. The punctate calcifications are non-specific and have been seen in a wide variety of disorders including the Zellweger syndrome, warfarin, dilantin, alcohol and rubella embryopathies, vitamin-K-epoxide-reductase deficiency, chromosome trisomies 18 and 21, the Smith-Lemli-Opitz syndrome, prenatal infectious chondritis, hypothyroidism, and other rare disorders. We report on a boy with short stature, developmental delay, nasal hypoplasia, telebrachydactyly, hypoplastic genitalia, CDP, ichthyosis, hypoplastic genitalia, and a 46-X,+der(X),t(X;Y)(p22.31;q11.21), Y karyotype. Genomic DNA probe analysis was interpreted as showing that the translocation breakpoint was within the X-linked Kallmann syndrome gene. We review a current classification of these disorders that includes 3 well-defined single gene disorders. These include an autosomal recessive rhizomelic type with early lethality, an X-linked dominant type with presumed male lethality, and an X-linked recessive type that has only been described as part of a contiguous gene deletion syndrome.

Combined Goltz and Aicardi syndromes in a terminal Xp deletion: are they a contiguous gene syndrome?

We report on 2 girls with a terminal deletion of the short arm of chromosome X. They had microphthalmia, cloudy corneae, mild linear skin lesions, and agenesis of corpus callosum. A comparison of clinical and cytogenetic findings in similar cases suggested that the critical genes for the Goltz and Aicardi syndromes might be contiguous in the region Xp22.31.

Short stature in a girl with a terminal Xp deletion distal to DXYS15: localisation of a growth gene(s) in the pseudoautosomal region

This report describes a Japanese girl with short stature and a rearranged X chromosome. Her height remained below the 3rd centile growth curve for Japanese girls, and her predicted adult height (148.5 cm) was below her target height (163 cm) and target range (155 to 171 cm). Cytogenetic studies showed that the rearranged X chromosome was formed by a breakage at q26 and a transfer of the Xq fragment onto the tip of Xp. The abnormal X was always late replicating. No mosaicism was detected. Molecular analysis showed an Xp terminal deletion distal to DXYS15. Biochemical and radiological studies for short stature disclosed no abnormality. On the basis of height analysis of previous reports and a genotype-phenotype correlation of this patient, we propose that a growth gene(s) is present in the distal part of the pseudoautosomal region.