Novel (CA)n marker DXYS241 on the nonrecombinant part of the human Y chromosome

The origin of modern humans can be traced by comparing polymorphic sites in either mitochondria or genomic sequences between humans and other primates. The human Y chromosome has both a non-recombining region and X-Y homologous pseudo-autosomal regions. In the nonrecombining region events during evolution can be directly detected. At least a part of homology between Xq21 and Yp11 is a result of rather recent translocations from the X chromosome to the Y chromosome. DNA markers residing in the nonrecombining region of the human Y chromosome are potentially useful in tracing male-specific gene flow in human evolution. However, the number of available markers in the region is limited. Here, we report a novel X-Y homologous (CA)n repeat locus in the nonrecombining region of the Y chromosome. This marker, DXYS241, has several interesting features. Y- and X-chromosome alleles are distinguishable because the Y-chromosome alleles are shorter than the X-chromosome alleles most of the time. We developed 2 primer sets for specific examination of Y- and X-chromosome alleles. The marker should be useful in establishing relationships between populations based on patrilineal gene flow. Sequences homologous to DXYS241 are also found on the X chromosome of primates. Four events during primate evolution that led to the modern human Y chromosome were identified.

Polymerase chain reaction analysis of the Y chromosome long arm in azoospermic patients: lack of the Y chromosome recognition motif (YRRM1) gene

We analyzed DNA from a patient with azoospermia whose Y chromosome was cytogenetically normal. A total of 16 loci on the Y chromosome long arm were examined: 15 loci between DYS7E and DYZ1, and the Y chromosome RNA recognition motif (YRRM1) locus, a candidate gene for the azoospermic factor AZF. We did not detect the YRRM1 gene in this patient. This finding supports the theory that YRRM1 is an essential gene for spermatogenesis.

An ancient retrotransposal insertion causes Fukuyama-type congenital muscular dystrophy

Fukuyama-type congenital muscular dystrophy (FCMD), one of the most common autosomal recessive disorders in Japan (incidence is 0.7-1.2 per 10,000 births), is characterized by congenital muscular dystrophy associated with brain malformation (micropolygria) due to a defect in the migration of neurons. We previously mapped the FCMD gene to a region of less than 100 kilobases which included the marker locus D9S2107 on chromosome 9q31. We have also described a haplotype that is shared by more than 80% of FCMD chromosomes, indicating that most chromosomes bearing the FCMD mutation could be derived from a single ancestor. Here we report that there is a retrotransposal insertion of tandemly repeated sequences within this candidate-gene interval in all FCMD chromosomes carrying the founder haplotype (87%). The inserted sequence is about 3 kilobases long and is located in the 3' untranslated region of a gene encoding a new 461-amino-acid protein. This gene is expressed in various tissues in normal individuals, but not in FCMD patients who carry the insertion. Two independent point mutations confirm that mutation of this gene is responsible for FCMD. The predicted protein, which we term fukutin, contains an amino-terminal signal sequence, which together with results from transfection experiments suggests that fukutin is a secreted protein. To our knowledge, FCMD is the first human disease to be caused by an ancient retrotransposal integration.

YAC and cosmid contigs encompassing the Fukuyama-type congenital muscular dystrophy (FCMD) candidate region on 9q31

Fukuyama-type congenital muscular dystrophy (FCMD), the second most common form of childhood muscular dystrophy in Japan, is an autosomal recessive severe muscular dystrophy associated with an anomaly of the brain. We had mapped the FCMD gene to an approximately 5-cM interval between D9S127 and D9S2111 on 9q31-q33 and had also found evidence for linkage disequilibrium between FCMD and D9S306 in this candidate region. Through further analysis, we have defined another marker, D9S172, which showed stronger linkage disequilibrium than D9S306. A yeast artificial chromosome (YAC) contig spanning 3,5 Mb, which includes this D9S306-D9S172 interval on 9q31, has been constructed by a combination of sequence-tagged site, Alu-PCR, and restriction mapping. Also, cosmid clones subcloned from the YAC were assembled into three contigs, one of which contains D9S2107, which showed the strongest linkage disequilibrium with FCMD. These contigs also allowed us to order the markers as follows: cen-D9S127-(approximately 800 kb)-D9S306 (identical to D9S53)-(approximately 700 kb)-A107XF9-(approximately 500 kb)-D9S172-(approximately 30 kb)-D9S299 (identical to D9S774)-(approximately 120 kb)-WI2269-tel. Thus, we have constructed the first high-resolution physical map of the FCMD candidate region. The YAC and cosmid contigs established here will be a crucial resource for identification of the FCMD gene and other genes in this region.

A novel (CA)n polymorphism on 6p21.1-21.2

A novel highly polymorphic CA repeat locus D6S2213 was identified on human chromosome 6p21.1-21.2. It should be a useful marker for linkage studies on chromosome 6 and also in forensic use.

Linkage-disequilibrium mapping narrows the Fukuyama-type congenital muscular dystrophy (FCMD) candidate region to <100 kb

Fukuyama-type congenital muscular dystrophy (FCMD), the second most common form of muscular dystrophy in Japan, is an autosomal recessive severe muscular dystrophy associated with brain anomalies. After our initial mapping of the FCMD locus to chromosome 9q31-33, we have further defined the locus within a approximately 5-cM region between D9S127 and D9S2111 and have found linkage disequilibrium between FCMD and D9S306 in this candidate region on 9q31. The high prevalence of FCMD among the Japanese, who are a relatively isolated population, provides an opportunity to utilize linkage-disequilibrium mapping. We developed three new microsatellites, near D9S306, from the FCMD YAC contig, determined their positions on YACs, and performed linkage-disequilibrium mapping with these markers and other newly published loci. The maximum value of p(excess), which represents the strength of linkage disequilibrium, was obtained at D9S2107; and this value showed a relatively steady rise and fall across the region that is likely to contain FCMD. Distances between FCMD and each marker were presumed to be approximately 1 Mb, approximately 350 kb, approximately 140 kb, approximately 20 kb, approximately 280 kb, approximately 450 kb, and approximately 740 kb for D9S306, A107XF9, D9S2105, D9S2107, D9S172, D9S299, and D9S2109, respectively. Haplotype analysis using the three closest markers D9S2105, D9S2107, and D9S172 indicated that most FCMD-bearing chromosomes are derived from a single ancestral founder and suggested that these markers can be used for the diagnosis of sporadic FCMD. Thus, the FCMD gene is most likely to lie within a region of <100 kb containing D9S2107.

Long Y-associated (GATA)n alleles were observed in a few ethnic groups in Asia

A Y-associated polymorphic locus, DYS19, was analyzed in a few ethnic groups in Asia and compared with that in Caucasians and Negroes. The locus contains 4-nucleotide repeats, (GATA)n, and the length of the repeated segments can be determined by the polymerase chain reaction (PCR). The predominant allele was 202 bp followed by 198 bp in all the 3 Asian populations examined. Long repeats that were rare in other populations were found more frequently in these Asian populations.

Sex reversal in a child with duplication of sex reversing locus on the short arm of the X chromosome (Xp)

We report a child with a female phenotype possessing a karyotype of 46,XY,13p+. The child had female external genitalia, and manifested severe mental retardation, pulmonary atresia and multiple congenital abnormalities. Laparoscopy revealed the presence of streak gonads and Müllerian structures. Histological examination of the gonads showed ovarian-like stroma with immature seminiferous tubules. Chromosome and gene analyses demonstrated Xp11.23 (or 11.3)-pter duplication and an intact sex determinating factor of Y (SRY). The findings of this case suggest that duplication of Xp causes sex reversal in the presence of SRY.

A unique origin and multistep process for the generation of expanded DRPLA triplet repeats

Dentatorubral and pallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disorder associated with the expansion of a CAG repeat at chromosome band 12p13. Epidemiological studies have demonstrated an increased prevalence of DRPLA in Japan, although several DRPLA kindreds of non-Japanese ancestry have been identified. To define the molecular basis for this geographic variation in prevalence, we have analyzed haplotypes around the repeat in several different ethnic groups. Two intragenic biallelic polymorphisms distinguished three haplotypes, each of which formed a predominant haplotype found in the three major racial populations. All the expanded repeats of Japanese and Caucasian patients studied were associated with a particular haplotype, which otherwise was associated with longer repeats commonly found in Asians. Our results support a multi-step model for repeat expansion, and suggest that expanded DRPLA repeats may have evolved from an ancient chromosomal haplotype of Asian origin. We also propose that a combination of a highly polymorphic microsatellite marker with relatively stable biallelic markers in a range of PCR amplification is a powerful tool for studies on human genome diversity, which may reveal the ancient human migration and the formation of ethnic groups.

Pericentric inversion with a minute deletion of the Y chromosome in a severely oligozoospermic man

An apparent pericentric inversion of the Y chromosome in a severely oligozoospermic infertile patient is described. The karyotype was 46,X,inv (Y) (p11.2 q11.23). DNA analysis, however, revealed a deletion involving nine loci within the most distal part of the euchromatic region of the long arm.

Chromosomal localisation of a Y specific growth gene(s)

Although a Y specific growth gene(s) has been postulated in the Yq11 region, the precise location has not been determined. To localise the growth gene(s), we correlated genotype with stature in 13 Japanese and four European non-mosaic adult male patients with a partial Yq deletion. Fourteen patients preserving the region between DYS11 and DYS246 did not have short stature (11 Japanese, 165-180 cm; three Europeans, 165-173 cm) whereas the remaining three patients with the region deleted had short stature (two Japanese, both 159 cm; one European, 157 cm). The results suggest that the region defined by DYS11 at interval 5C and by DYS246 at interval 5D may be the critical region for the Y specific growth gene(s).

Evaluation of long-term results of Caroli's disease: 21 years' observation of a family with autosomal "dominant" inheritance, and review of the literature

A 5-year-old girl underwent laparotomy in 1972 because of hepatomegaly and mottled radiopacities shown by cholangiography. Polycystic segmental dilatation of the intrahepatic bile ducts, typical of Caroli's disease, was found. Thereafter she remained in good health for over 21 years with careful medical management. In 1972 mottled radiopacities of the hepatic parenchyma were also demonstrated by cholangiography in her 9-year-old brother, who, however, remained asymptomatic until hematemesis due to esophageal varices suddenly occurred in 1993. At the time of the pre-operative evaluation for esophageal transection, his condition was definitively diagnosed as Caroli's disease. Their father was in good health, but in 1993 was shown by CT to have the same disease. The mode of inheritance is likely to be autosomal dominant, although Caroli's disease or congenital hepatic fibrosis is generally considered autosomal recessive (McKusick number 263200) (1). If we had not examined the father, this particular family would have been accepted as an example of autosomal recessive inheritance. We suggest that further family studies are needed to exclude the autosomal dominant mode of inheritance, and that at least some of the recessive cases in the literature are, in fact, autosomal dominant. Well-documented cases of "classical" Caroli's disease in the literature were reviewed with special reference to the long-term results. In addition, an international questionnaire aimed at establishing the further clinical course of the patient was sent to authors who reported cases after 1968.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic identity of Fukuyama-type congenital muscular dystrophy and Walker-Warburg syndrome

Both Fukuyama-type congenital muscular dystrophy (FCMD) and Walker-Warburg syndrome (WWS) are unusual genetic syndromes consisting of congenital muscular dystrophy and complex malformations of the brain and eye. It has been intensively discussed whether FCMD and WWS belong to the same disease entity or not. We analyzed a family in which 3 siblings were affected with either FCMD or WWS by using polymorphic microsatellites flanking the FCMD locus on chromosome 9q31-33. The results suggested that both FCMD and WWS siblings shared the identical combination of mutations on either allele of the FCMD locus. FCMD and WWS could be "genetically" identical.

Monozygotic twins of different apparent sex

We report on twins of unlike sex who shared a 45,X/46,X,+mar karyotype. The mar chromosome was found to be Yq- by DNA analysis. Marker studies, including 8 VNTR loci, yielded a probability of monozygosity of 0.99999996.

The CpG island of the FMR-1 gene is methylated differently among embryonic tissues: implication for prenatal diagnosis

We studied the methylation status of the CpG island of the FMR-1 (fragile X syndrome) gene to recognize the possibility of its prenatal diagnosis with early pregnant subjects. Southern hybridization using EcoRI/BssHII restriction enzymes double digestion was performed in the brain and chorionic villi of 8th week embryos, and the placenta and cord blood of newborns. No methylation of the FMR-1 gene occurred in both of the tissues examined in males, while 50% of the cells in females were methylated in both the brain and the cord blood, indicating that methylation occurs with inactivation of the X-chromosome in accordance with the literature. However, there was no methylation in either the chorionic villi or placenta in female as well as in males. Some extra-embryonic tissues such as the chorionic villi and the placenta escape X-chromosome FMR-1 gene inactivation and it can be the exception in the lyonization. To assess the methylation status in prenatal diagnosis, precautions are needed and they are not suitable for prenatal diagnosis.

Intact sex determining region Y (SRY) in a patient with XY pure gonadal dysgenesis and a twin brother

A patient with an apparently normal 46, XY karyotype, suffering from pure gonadal dysgenesis and of short stature was investigated. The patient, who was growth retarded, was a 30-year-old married Japanese woman with a history of primary amenorrhea and infertility with a weight of 42 kg and a height of 146 cm. She has a phenotypically and karyotypically normal dizygotic twin brother with normal development. Southern-blot and polymerase chain-reaction analyses revealed no apparent deletions in the patient's Y chromosome, including the sex-determining region Y (SRY). The DNA sequencing of the SRY gene showed a 100% nucleotide sequence identity with the reported cloned sequence. Sex reversal in the present case may be due to mutation at a locus other than SRY in the sex determining pathway, a gene potentially involved in the determination of human constitution.

Myoclonic epilepsy and a maternally derived deletion of 15pter-->q13

Deletion of a 15pter-->q13 segment of maternal origin was observed in a mentally retarded infant. In addition to the symptoms common to deletions of proximal 15q, the phenotype included myoclonic epilepsy of early infantile onset. The deletion was caused by a 3:1 disjunction in the mother, who was a carrier of t(15;22)(13q;p11) translocation.

[Human Y chromosome in reproduction and development]

The present status of human Y chromosome study is reviewed. A total of 13 genes, including two pseudogenes, have been mapped on the Y chromosome. They included colony stimulating factor receptor (CSF2R), SRY (TDF), ZFY, RPS4Y (ribosome protein 4S), ADMLY (Kallman syndrome), AMGL (amelogenin, which we cloned ourselves) and so on. In addition, the presence of two XY homologous genes is proposed. One increases performance IQ and the other reduces water-content of an embryo. We examined 54 azoospermic patients with an apparently normal Y chromosome. Each patient was analyzed for the presence or absence of 26 loci on the Y chromosome. Six showed a very small "micro" deletion. A common segment which is absent in every 6 patient has been identified. Cloning of azoospermia-related gene is being attempted using YAC clones.

Sex identification by polymerase chain reaction using a Y-autosome homologous primer set

We have developed a one-step polymerase chain reaction (PCR) technique which detects a sequence on the human Y chromosome and an autosomal sequence in one reaction. The method is very reliable for the sex determination, as the detection of the autosome-specific signal ensures the presence of DNA in the specimen even in the absence of the Y-specific signal.

11q trisomy detected by fluorescence in situ hybridization

A patient with psychomotor developmental delay, multiple minor anomalies, congenital heart disease and left inguinal hernia is reported. His karyotype was 45,X/46,X,+mar (3:37 cells), and the marker chromosome was identified as t(Y;11)(q12;q14?) using fluorescence in situ hybridization and fluorescent chromosome painting. He was diagnosed as mosaic for de novo 11q trisomy.

A minute deletion of the Y chromosome in men with azoospermia

We analyzed deoxyribonucleic acid from 50 Japanese men with azoospermia whose Y chromosomes were cytogenetically normal. A total of 26 loci was examined in each patient. Of these patients 6 had small interstitial deletions, each of which was located within the distal part of Yq11. Five of these 6 patients lacked the same 2 loci, DYS7C and DYS1, while 1 patient had a larger deletion including DYS7C but not DYS1. More than 10% of all men with azoospermia of unknown origin may have minute interstitial deletions of the Y chromosome surrounding the DYS7C locus. The proximal part of this zone presumably encompasses the gene deletion that causes azoospermia.

Restriction fragment length polymorphisms of the CYP11B1 gene in the Japanese population

Restriction fragment length polymorphisms (RFLPs) of the CYP11B1 gene were studied in Japanese using cDNA clone P450c11 as a probe. Genomic DNAs from 60 unrelated Japanese individuals were digested with 8 different restriction enzymes and analyzed by Southern blot hybridization. Two RFLPs were detected in MspI digests of the DNA. One (A) was characterized by polymorphic bands at 3.4 and 2.5 kilobase-pairs (kb) and the other (B) by polymorphic bands at 1.7 and 1.2 kb. The third RFLP was observed in PvuII-digested samples and was polymorphic at 5.8 and 4.0 kb bands. Two of the three RFLPs found, RFLP (A) and (C), have not been described in the only previous report which was based on Caucasian samples. We also examined the RFLPs of a 3 generation family of 11 beta-hydroxylase deficiency caused by an abnormality of the CYP11B1 gene. All the family members were homozygous in all three RFLPs and was thus not informative.

Detection of the testis determining factor in an XX man

An XX male patient was examined for the presence of 25 loci on the Y chromosome. Only 2 loci, the proximal border of the pseudoautosomal region Y and the sex determining region Y, were detected in this patient. The other 23 loci, including the zinc finger protein Y, were absent. We presume that a crossing over between the X and Y chromosomes occurred at the region proximal to the sex determining region Y but distal to the zinc finger protein Y during meiosis of the father.

Cytogenetical and molecularbiological studies on a bovine XY female

A bovine XY female in Holstein-Friesian heifer, which appeared as female with uterus and ovaries but did not show the estrus until 23 months old after the birth, was cytogenetically and molecularbiologically examined. As results of chromosome analysis, leucocyte and fibroblasts from skin, spleen and kidney examined had only metaphase plates with 60, XY. From these results and the clinical characteristics, this case was clearly diagnosed as a pure XY female. It was ascertained that the two genes, ZFY and AMG gene which located on the short arm of the Y chromosome (Yp) were detected in normal bulls and a XY female, but were not detected in normal cow, mother cow and half-sib heifer by Southern blotting.

Localization of 24 cosmid clones on the human Y chromosome

Twenty-four novel cosmid clones were cloned and mapped on the human Y chromosome using a panel consisting of DNA from seven individuals each having a different segment of the Y chromosome. Eight were assigned to the short arm, 15 to the long arm and 1 to the both short and long arms.

A Y-associated allele may be characteristic of certain ethnic groups in Asia

The probe 47z detects DNA polymorphisms on both the X and Y chromosomes. Blood samples were collected from Korean, Chinese, Jewish, Caucasian and Negro populations and polymorphisms of both loci were compared with findings previously reported in Japanese. Both Y1 and Y2 alleles were detected in Japanese and Koreans. However, only the Y1 allele was detected in each of the other populations. Although, both X1 and X2 alleles were detected in all examined populations, the frequency of the X2 allele was very low among Negroes.

PCR detection of structurally abnormal Y chromosomes

Three probes each detecting a locus on the proximal long arm of the Y chromosome were partially sequenced. Thus, 3 sets of novel primers were developed which enable PCR detection of these 3 loci. Five previously reported primer sets, 3 on the short arm and each one on the centromere and the distal long arm, were mapped along with the novel three using a mapping panel consisted of 8 patients each with different structural abnormality of the Y chromosome. Now, PCR detection of these 8 loci covering an entire length of the Y chromosome has become possible enabling rapid screening of patients with Y chromosome aberrations.

Normal Y sequences in Smith-Lemli-Opitz syndrome with total failure of masculinization

We report an infant with characteristics of Smith-Lemli-Opitz syndrome who had anteverted nostrils, apparently low-set ears, micrognathia, high-arched palate, cleft palate, growth and psychomotor retardation, hypotonia, poor suck, cerebral hypotrophy and double renal pelvis and ureter. An EEG showed spike waves in the right temporal area. The patient appeared to have normal internal and external genitalia of the female type. Both ovaries were dysplastic. The karyotype was 46,XY. All of 26 loci on the Y chromosome were positive including SRY, a candidate gene for TDF.

DNA analysis of two patients with a non-fluorescent Y chromosome

Results of DNA study on two patients of gonadal dysgenesis with a 45,X/46,X,Ynf (non-fluorescent Y chromosome) karyotype are described. In one patient who developed gonadoblastoma, all 12 loci on the non-fluorescent part of Yq were detected. Another patient did not have gonadoblastoma at 20 years, and only the proximal 6 loci out of 12 were detected.

Deoxyribonucleic acid study on 2 XX male patients

Two XX male patients were examined for the presence of 25 Y-specific loci using Southern blot analysis and polymerase chain reaction techniques. They were phenotypically normal male patients, although 1 had bilateral undescended testes and 1 had hypoplastic testes. The former patient had 10 of 11 loci on the short arm, while the latter lacked any of the 25 Y-specific loci. These findings may suggest the existence of a non-Y gene that is controlled by the testis-determining factor on the short arm of the Y chromosome and has a role in the testis formation in man.

Sex determination of forensic samples by dual PCR amplification of an X-Y homologous gene

Sex determination by polymerase chain reaction (PCR) analysis of the X-Y homologous amelogenin gene is highly reliable since the detection of an X-specific amplified fragment validates the procedure. Previously, we reported that 250 ng of template DNA are required for sex determination by this method. We report here a refinement of the technique to include dual PCR. Dual PCR using two sets of primers results in the detection of X- and Y-specific amplified fragments from as little as 0.005 ng of template DNA. This is a powerful technique for the analysis of trace forensic samples and its application is discussed.

Deoxyribonucleic acid and cytological detection of Y-containing cells in an XX hypospadiac boy with polyorchidism

A hypospadiac boy with a hypoplastic penis and an apparent 46,XX karyotype in blood and testis cultures is described. Exploratory laparotomy and bilateral gonadal biopsy revealed the presence of 2 testes in the right and 1 in the left hemiscrotum, each of which only showed hypoplastic testicular tissues histologically. Uncultured testis smears showed Y chromatin in approximately 20% of the cells. Also, the Southern blot and polymerase chain reaction analyses detected a weak but distinct signal of Y chromosome-derived deoxyribonucleic acid sequences in the perineal skin but not in the blood lymphocytes. The results indicated that the boy had a small proportion of Y chromosome-containing cells in the form of mosaicism in limited tissues, such as the testes and perineal skin. This finding may have implications in the genesis of testes in some cases of XX patients, and true hermaphrodites or male pseudohermaphrodites with an apparent 46,XX karyotype. To our knowledge, this appears to be the first case of polyorchidism with an identified chromosome abnormality.

PCR detection of distal Yp sequences in an XX true hermaphrodite

An XX true hermaphrodite was examined for the presence of Y-specific sequences using Southern-blotting and polymerase chain reaction (PCR) techniques. Of 25 loci examined, only two, the proximal border of the pseudoautosomal region (PABY) and the sex determining region of the Y chromosome (SRY), were detected. A crossing over event in paternal meiosis, proximal to the SRY locus but distal to the zinc finger protein (ZFY) locus, presumably transferred to two loci to the X chromosome.

Diagnosis of twin zygosity by hypervariable RFLP markers

The application of variable number of tandem repeat (VNTR) markers to the determination of twin zygosity was investigated. In the first case, which was performed with the use of six VNTR markers, the probability of monozygosity, calculated from Essen-Möller's formula II, was 0.99972. In the other three cases in which four VNTR markers were analyzed, the probabilities were 0.98251-0.99557. These results suggest that VNTR markers are useful for determination of twin zygosity.

Absence of fetal cells in maternal circulation at a level of 1 in 25,000

A dual polymerase chain reaction (PCR) technique is developed which enables the detection of one part male DNA in 25,000 parts female DNA. The technique amplifies a part of the X-Y homologous amelogenin gene in which the Y counterpart has a 189 bp deletion within one of the introns. This deletion has made it possible to identify individual X and Y counterparts based on the difference in size between them. None of the 18 pregnant women studied showed a positive Y-signal although eight of them bear male fetuses excluding the presence of fetal cells at one in 25,000 maternal cells. The results presented here show that a sensitivity of greater than one in 25,000 is required for detection of fetal genetic disease using maternal peripheral blood.

A deletion in the amelogenin gene (AMG) causes X-linked amelogenesis imperfecta (AIH1)

Amelogenesis imperfecta is characterized by the defective formation of tooth enamel. Here we present evidence that the X-linked form of this disorder (AIH1) is caused by a structural alteration in one of the predominant proteins in enamel, amelogenin. Southern blot analysis revealed a deletion extending over 5 kb of the amelogenin gene in males with the hypomineralization form of the AIH1. Carrier females were heterozygous for the molecular defect. The deletion appears to include at least two exons of the amelogenin gene and the extent of the deletion was verified by PCR analysis. The mutation was shown to segregate with the disease among 15 analyzed individuals belonging to the same kindred. Our results link a defect in the amelogenin gene to the abnormal formation of enamel. We thus conclude that the amelogenin protein has a role in biomineralization of tooth enamel.

Sex identification by polymerase chain reaction using X-Y homologous primer

A method of sex identification using the polymerase chain reaction technique is described. Using a pair of nucleotide primers from an X-Y homologous region, both the X and the Y sequences can be amplified simultaneously, and more importantly, they result in fragments of different lengths. The success of the procedure is therefore monitored by the presence of a X-specific band while sex is identified by the presence or absence of a Y-specific band.

DNA analysis of a patient with two different marker chromosomes using Y-specific DNA probes

A female patient with unilateral gonadal dysgenesis was a mosaic for three cell lines, 45,X/46,X, + marI/46,X, + marII, including two different marker chromosomes. DNA analysis using 17 Y-specific DNA probes revealed that each marker consists of different segments of the Y chromosome.

DNA hybridization study using Y-specific probes in an XX-male

A 30-year-old male attended the Toyama Medical and Pharmaceutical University Hospital with the chief complaint of infertility. Physical examination showed bilateral small testes and the semen contained no sperm. Hormonal studies revealed hypergonadotropic hypogonadism and cytogenetic studies showed a 46,XX karyotype. High-resolution banding showed no abnormalities in both of the X chromosomes. Histological examination of both testes showed germinal aplasia and the proliferation of Leydig cells. The diagnosis of XX-male was made from the above findings. A DNA hybridization study using 17 Y-specific probes revealed the presence of a major part of the short arm of the Y chromosome, which had presumably been translocated to the X chromosome. The translocated Y short arm had a small deletion within it.