Prenatal diagnosis, sonographic findings and molecular genetic analysis of a 46,XX/46,XY true hermaphrodite chimera

Molecular Analysis of Parthenogenetic Chimerism in a 46,XX/46,XY Patient with Idiopathic Oligoasthenoteratozoospermia

INTRODUCTION

Parthenogenetic chimera is an extremely rare condition in human. Very few patients with parthenogenetic chimerism with XX/XY cells have been identified.

CASE PRESENTATION

We report the clinical findings and molecular analysis of chimerism with a 46,XX/46,XY karyotype in a patient presenting idiopathic oligoasthenoteratozoospermia (OAT). To clarify the mechanism of chimera formation, short tandem repeat analysis using 21 loci was carried out. Quantitation of alleles in D6S1043, D12S391, fibrinogen alpha chain, and amelogenin revealed double paternal and one maternal genetic contribution to the patient, which is consistent with a parthenogenetic chimerism. The likely mechanism of chimerism formation was also discussed, followed by a literature review.

CONCLUSION

This is the first documented case of parthenogenetic chimerism in an adult male with XX/XY cells presenting OAT. Improved cell sampling and more sensitive and specific detection methods are necessary to identify more patients with XX/XY chimerism for systematic studies on this condition in the future.

Natural human chimeras: A review

The term chimera has been borrowed from Greek mythology and has a long history of use in biology and genetics. A chimera is an organism whose cells are derived from two or more zygotes. Recipients of tissue and organ transplants are artificial chimeras. This review concerns natural human chimeras. The first human chimera was reported in 1953. Natural chimeras can arise in various ways. Fetal and maternal cells can cross the placental barrier so that both mother and child may become microchimeras. Two zygotes can fuse together during an early embryonic stage to form a fusion chimera. Most chimeras remain undetected, especially if both zygotes are of the same genetic sex. Many are discovered accidently, for example, during a routine blood group test. Even sex-discordant chimeras can have a normal male or female phenotype. Only 28 of the 50 individuals with a 46,XX/46,XY karyotype were either true hermaphrodites or had ambiguous genitalia. Blood chimeras are formed by blood transfusion between dizygotic twins via the shared placenta and are more common than was once assumed. In marmoset monkey twins the exchange via the placenta is not limited to blood but can involve other tissues, including germ cells. To date there are no examples in humans of twin chimeras involving germ cells. If human chimeras are more common than hitherto thought there could be many medical, social, forensic, and legal implications. More multidisciplinary research is required for a better understanding of this fascinating subject.

Chimerism in health and potential implications on behavior: A systematic review

In this review, we focus on the phenomenon of chimerism and especially microchimerism as one of the currently underexplored explanations for differences in health and behavior. Chimerism is an amalgamation of cells from two or more unique zygotes within a single organism, with microchimerism defined by a minor cell population of <1%. This article first presents an overview of the primary techniques employed to detect and quantify the presence of microchimerism and then reviews empirical studies of chimerism in mammals including primates and humans. In women, male microchimerism, a condition suggested to be the result of fetomaternal exchange in utero, is relatively easily detected by polymerase chain reaction molecular techniques targeting Y-chromosomal markers. Consequently, studies of chimerism in human diseases have largely focused on diseases with a predilection for females including autoimmune diseases, and female cancers. We detail studies of chimerism in human diseases and also discuss some potential implications in behavior. Understanding the prevalence of chimerism and the associated health outcomes will provide invaluable knowledge of human biology and guide novel approaches for treating diseases.

A parthenogenetic maternal and double paternal contribution to an ovotesticular disorder of sex development

BACKGROUND

An ovotesticular disorder of sex development (OT-DSD) was rarely found in human. The mechanism causing such condition is poorly understood. We hereby reported a 11-year-old child with OT-DSD and a karyotype 46,XX/46,XY, a single maternal and double paternal genetic contribution to the patient.

RESULTS

Fluorescence in situ hybridization (FISH), blood grouping, HLA (human leukocyte antigen) haplotyping and a genome-wide scanning of lymphocytes with 398 short tandem repeat microsatellite markers were performed to investigate the origin of the cell lines concerned. ABO typing revealed that two populations of red cells were in the patient, which were group A and group B, both from paternal alleles. HLA haplotyping showed the patient had three haplotypes. Haplotype 1 was inherited from maternity, haplotype 2 and 3 were from paternity. The STR microsatellite analysis showed 25 of the 74 fully informative markers in both parents, three alleles were inherited: one of them was from mother, another two were from father. Seventeen of the thirty-eight paternal markers, the patient inherited two paternal alleles. For 121 informative maternal markers, the patient had a single maternal allele. There were two distinct alleles in locus DXS6810 and DXS1073 on X-chromosome, in which one was from the mother and the other from the father.

CONCLUSIONS

The patient was a single maternal and double paternal genetic, which was a type of a parthenogenetic division of a maternal haploid nucleus into two identical nuclei, followed by fertilization by two spermatozoa and fusion of the two zygotes into a single individual at the early embryonic stage. To the best of our knowledge, this is the oldest OT-DSD case of parthenogenetic chimerism. These data provide additional evidence that a parthenogenetic maternal and double paternal contribution causes 46,XX/46,XY OT-DSD.

Sex chromosomes and sex chromosome abnormalities

This article focuses on constitutional sex chromosome abnormalities detected by conventional cytogenetics and fluorescence in situ hybridization. The author discusses the two general classifications of abnormalities: numerical and structural. Also included are descriptions of unique aspects of X and Y chromosomes, technological advances in detection, and future perspectives.

Rare cases of disorders of sex development (DSD) in adolescents with female phenotype

BACKGROUND

Disorders of sex development (DSD) belong to uncommon pathologies; in addition, there are especially rare forms, such are ovotesticular disorders (OT), Turner syndrome and early malignisation of intraabdominal located gonads in the cases of androgen insensitivity syndrome.

OBJECTIVE

In this article we present four rare cases of DSD in female phenotype adolescents: two cases of ovotesticular DSD with 46,XX and 46,XY karyotypes; one familial case of androgen insensitivity syndrome (AIS) with early malignancy (19-year-old) of intra-abdominally-located testicle in older siblings, and a case of spontaneous menstruation in a patient with Turner syndrome and mosaic karyotype 45,X/47,XXX. Rare cases of DSD are connected with diagnostic and management difficulties and so description of each such case and collection of data in this field is very important from a scientific, as well as a practical, point of view. Determination of prognosis and adequate management of each individual patient are also essential. Study of this issue is especially sensitive in the case of adolescent patients in order to avoid physiological stress, to reduce health risks and to improve quality of life.

Chimerism in black southern African patients with true hermaphroditism 46,XX/47XY,+21 and 46,XX/46,XY

True hermaphroditism is defined by the presence of both testicular and ovarian tissue in an individual. True hermaphrodites usually present at birth with ambiguous genitalia, and subsequent invasive investigations are needed to confirm the diagnosis. Several large cohorts of black South Africans with true hermaphroditism have been described, and by far the majority of those investigated had a 46,XX karyotype, with absence of the SRY sequence. This paper represents the first report of the molecular investigation of mosiacism/chimerism as the cause of hermaphroditism in black southern African patients. It is the second report worldwide of a 46,XX/47,XY,+21 chimera, with the first described in a Japanese infant in 1994. Case 1 in the present study is a child who is a 46,XX/47,XY,+21 tetragametic chimera. Molecular studies revealed two paternal and two maternal alleles at four of ten STR loci investigated and three alleles at four of these loci. The young boy exhibited no features of Down syndrome, other than a unilateral single palmar crease. Cases 2 and 3 both have a 46,XX/46,XY karyotype. Chimerism is supported by molecular analysis in Case 2, and molecular studies were not done for Case 3.

Origin and outcome of pregnancies affected by androgenetic/biparental chimerism

BACKGROUND

Androgenetic diploid cells confined to the placenta have recently been reported in several cases of normally developed fetuses in association with placental mesenchymal dysplasia (PMD).

METHODS AND RESULTS

We investigated two singleton, mildly growth-restricted, female pregnancies ascertained on the basis of PMD. One case had liver hemangiomas and both infants had multiple skin hemangiomas. Post-natal development was normal. Molecular marker analysis confirmed the diagnosis of androgenetic and normal mixed cell populations in the placenta. Both cases derived from a single maternal genome (M1) and two distinct paternal genomes (P1 and P2). In one case, the androgenetic cell population contained both paternal genomes (P1P2), with one shared in common with the biparental (M1P1) population. In the second case, the androgenetic lineage showed complete homozygosity (P2P2) for a paternal genome not common to the biparental cell population.

CONCLUSION

These new PMD cases help to define the range of possible clinical presentations of androgenetic/biparental mosaicism or chimerism. Placentas with androgenetic/biparental chimeric cell populations may derive from a single tri-pronuclear (3PN) zygote in which one or more parental genomes are not equally apportioned to the daughter cells in the first cell division.

Chimera and other fertilization errors

The finding of a mixture of 46,XX and 46,XY cells in an individual has been rarely reported in literature. It usually results in individuals with ambiguous genitalia. Approximately 10% of true human hermaphrodites show this type of karyotype. However, the underlying mechanisms are poorly understood. It may be the result of mosaicism or chimerism. By definition, a chimera is produced by the fusion of two different zygotes in a single embryo, while a mosaic contains genetically different cells issued from a single zygote. Several mechanisms are involved in the production of chimera. Stricto sensu, chimerism occurs from the post-zygotic fusion of two distinct embryos leading to a tetragametic chimera. In addition, there are other entities, which are also referred to as chimera: parthenogenetic chimera and chimera resulting from fertilization of the second polar body. Furthermore, a particular type of chimera called 'androgenetic chimera' recently described in fetuses with placental mesenchymal dysplasia and in rare patients with Beckwith-Wiedemann syndrome is discussed. Strategies to study mechanisms leading to the production of chimera and mosaics are also proposed.

Persistent gestational trophoblastic disease after an androgenetic/biparental fetal chimera: a case report and review

We present a case of a dichorionic/diamniotic twin pregnancy in which one twin presented with ultrasound findings suggestive of molar changes in the placenta. The placenta of twin A seemed to be grossly enlarged and cystic, and twin A was small for gestation. After an inevitable abortion, a detailed histological and genetic evaluation was performed on the fetus and placenta from twin A, including traditional cytogenetic techniques, microsatellite marker analysis, fluorescent in situ hybridization, and p57 immunostaining. It was determined that twin A was a chimera with a biparental XX cell line and an androgenetic XY cell line. The 2 cell lines were present in both the placenta and the fetus. The patient later developed and was treated for persistent gestational trophoblastic disease, which has been shown to have an increased risk after an androgenetic conception. Cases of mosaicism or chimerism involving an androgenetic cell line may be difficult to diagnose histologically but are critical to identify because of the increased risk for persistent gestational trophoblastic disease. Therefore, we emphasize the importance of using multiple molecular, cytogenetic, and immunohistochemical techniques when diagnosing cases involving such unusual placental abnormalities. To our knowledge, this is the first reported case of persistent gestational disease after a fetal chimera.

Prenatal Diagnosis and Genetic Analysis of a Fetus with 47,XX, +21/46,XX Mosaicism and XX/XY Chimerism

Prenatal diagnosis of simultaneous occurrence of chimerism and autosomal mosaicism is extremely rare. We report the prenatal diagnosis and genetic analysis of a fetus in a twin pregnancy with mosaic 47,XX,+21/46,XX with chimeric XX/XY. A 36-year-old, para 1, woman was referred for genetic counseling at 20 weeks' gestation because of abnormal karyotype (47,XX,+21/46,XX) in one fetus in a twin pregnancy. Cordocentesis revealed 47,XX,+21[3]/46,XX[35]/46,XY[7] in this fetus. Postnatal cytogenetic analysis of cord blood confirmed three cell lines in this twin (A) and 46,XY in the co-twin (B). Postmortem pathologic findings of both fetuses were normal. Fluorescence in situ hybridization identified three cell lines in the cord blood of twin A. Molecular genetic analysis using polymorphic DNA markers revealed parental origin of fetal tissue, and confirmed the chimeric status. Molecular genetic analysis with polymorphic DNA markers help to differentiate chimerism from mosaicism and define the origin of cell lines, which may have importance in genetic counseling.