ANALYSIS OF HOMEOBOX GENE HOXA10 MUTATIONS IN CRYPTORCHIDISM

Genetics of cryptorchidism and testicular regression

Cryptorchidism, i.e., undescended testis, is one of the most common genital malformations in newborn male babies. The birth rate of cryptorchidism varies from 1.6 to 9.0 %. Etiology of disrupted testicular descent is complex and predisposing causes include genetic, hormonal, environmental, lifestyle and maternal factors. Testicular descent occurs in two major steps and testicular hormones and normal function of hypothalamic-pituitary-testicular axis are important for normal descent. Several gene mutations are associated with syndromic cryptorchidism but they are rarely found in boys with isolated undescended testis. Testicular regression can also cause an empty scrotum. Normal male genital phenotype indicates that the boy has had functioning testis during development. Torsion of the testis can cause testicular regression but in many cases the reason for vanishing testis remains elusive. In this narrative review we discuss genetics of cryptorchidism and testicular regression.

E2F1 regulates testicular descent and controls spermatogenesis by influencing WNT4 signaling

Cryptorchidism is the most common urologic birth defect in men and is a predisposing factor of male infertility and testicular cancer, yet the etiology remains largely unknown. E2F1 microdeletions and microduplications contribute to cryptorchidism, infertility and testicular tumors. Although E2f1 deletion or overexpression in mice causes spermatogenic failure, the mechanism by which E2f1 influences testicular function is unknown. This investigation revealed that E2f1-null mice develop cryptorchidism with severe gubernacular defects and progressive loss of germ cells resulting in infertility and, in rare cases, testicular tumors. It was hypothesized that germ cell depletion resulted from an increase in WNT4 levels. To test this hypothesis, the phenotype of a double-null mouse model lacking both Wnt4 and E2f1 in germ cells was analyzed. Double-null mice are fertile. This finding indicates that germ cell maintenance is dependent on E2f1 repression of Wnt4, supporting a role for Wnt4 in germ cell survival. In the future, modulation of WNT4 expression in men with cryptorchidism and spermatogenic failure due to E2F1 copy number variations may provide a novel approach to improve their spermatogenesis and perhaps their fertility potential after orchidopexy.

A Systematic Review of Anogenital Distance and Gynecological Disorders: Endometriosis and Polycystic Ovary Syndrome

BACKGROUND AND AIM

Anogenital distance (AGD) can serve as a life-long indicator of androgen action in gestational weeks 8-14. AGD has been used as an important tool to investigate the exposure to endocrine-disrupting compounds in newborns and in individuals with male reproductive disorder. Endometriosis and polycystic ovary syndrome (PCOS) are two common gynecological disorders and both are related to prenatal androgen levels. Therefore, we performed a systematic review to evaluate the relationships of AGD with these gynecological disorders.

METHODS

PubMed, Web of Science, and Embase were searched for published studies up to January 25, 2021. No language restriction was implemented.

RESULTS

Ten studies were included in this review. Five focused on women with endometriosis, and six investigated women with PCOS. According to these studies, PCOS patients had longer AGD than controls, while endometriosis patients had shorter AGD than controls. In conclusion, this study provides a detailed and accurate review of the associations of AGD with endometriosis and PCOS.

CONCLUSION

The current findings indicate the longer AGD was related to PCOS and shorter AGD was related to endometriosis. However, further well-designed studies are needed to corroborate the current findings.

Mutation profiles and clinical characteristics of Chinese males with isolated hypogonadotropic hypogonadism

OBJECTIVE

To investigate the mutation profiles and clinical characteristics of Chinese males with isolated hypogonadotropic hypogonadism (IHH) and discover new pathogenic genes that cause IHH.

DESIGN

A gene panel, including 31 known IHH genes and 52 candidate genes, was used to perform semiconductor next-generation sequencing.

SETTING

University hospital.

PATIENTS

One hundred thirty-eight sporadic male IHH patients and 10 IHH families; 100 healthy men with normal fertility served as control subjects.

INTERVENTIONS(S)

None.

MAIN OUTCOME MEASURE(S)

Targeted next-generation sequencing, polymerase chain reaction and sequencing, pedigree analysis, and bioinformatics analysis.

RESULT(S)

Variants were distributed uniformly throughout 52 genes (52/83, 62.65%), including 16 (16/31, 51.61%) causal genes and 36 (36/52, 69.23%) candidate genes. Six new pathogenic variants and 52 likely pathogenic variants were identified in 16 genes known to cause nIHH/KS (normosmic IHH/Kallmann syndrome). In the 148 probands, PROKR2 (22/148, 14.86%), CHD7, FGFR1, and KAL1 had high mutation rates, and 8.78% (13/148) of the patients carried at least two variants in known genes. In addition, variants were identified in 36 candidate genes, and EGFR, ERBB4, PAX6, IGF1, SEMA4D, and SEMA7A should be prioritized for further research and genetic testing in IHH.

CONCLUSION(S)

The mutation frequency of IHH-causal genes in Chinese HAN males was different from the data reported in white populations. Oligogenic inheritance was a common phenomenon in IHH. Our study expands the mutation profile for IHH, and the new likely pathogenic genes identified in our study warrant further research in GnRH neuronal networks.

Proximate cause, anatomical correlates, and obstetrical implication of a supernumerary lumbar vertebra in humans

OBJECTIVES

Three issues are considered on variation in number of presacral vertebrae (PSV) in humans: (1) sexual difference in number of PSV, (2) inactivation of Hoxd-11 gene as etiology for a supernumerary lumbar vertebra, and (3) anatomical correlates of a supernumerary lumbar vertebra, including lumbar-sacral nearthrosis, and pelvic size.

MATERIALS AND METHODS

Sample was 407 skeletonized females and 1,318 males from United States; ages at death were 20 to 49 years. Two subsamples of males were used: (1) 98 with modal numbers of cervical, thoracic, lumbar, and sacral vertebrae (PSV = 24) and (2) 45 with a supernumerary lumbar vertebra but modal numbers for other vertebral segments (PSV = 25). Measurements were taken of ulna, second metacarpal, vertebrae, femur, and pelvis; presence of lumbar-sacral nearthrosis was observed.

RESULTS

Although 90% of females and males have 24 PSV, females have higher frequency of 23 PSV and males have higher frequency of 25 PSV. Compared to males with 24 PSV, males with 25 PSV and supernumerary lumbar vertebra show (1) no difference in anatomies associated with inactivation of Hoxd-11, and (2) higher frequency of lumbar-sacral nearthrosis and smaller pelvic inlet circumference.

DISCUSSION

Sexual difference in number of PSV may be due to tempo of somite formation and Hox gene activation. Hypothesis is not supported that a supernumerary lumbar vertebra is due to inactivation of Hoxd-11. The presence of a supernumerary lumbar vertebra is associated with small pelvic inlet circumference, which can be obstetrically disadvantageous.

Risk factors for cryptorchidism

Undescended testis - known as cryptorchidism - is one of the most common congenital abnormalities observed in boys, and is one of the few known risk factors for testicular cancer. The key factors that contribute to the occurrence of cryptorchidism remain elusive. Testicular descent is thought to occur during two hormonally-controlled phases in fetal development - between 8-15 weeks (the first phase of decent) and 25-35 weeks gestation (the second phase of descent); the failure of a testis to descend permanently is probably caused by disruptions to one or both of these phases, but the causes and mechanisms of such disruptions are still unclear. A broad range of putative risk factors have been evaluated in relation to the development of cryptorchidism but their plausibility is still in question. Consistent evidence of an association with cryptorchidism exists for only a few factors, and in those cases in which evidence seems unequivocal the factor is likely to be a surrogate for the true causal exposure. The relative importance of each risk factor could vary considerably between mother-son pairs depending on an array of genetic, maternal, placental and fetal factors - all of which could vary between regions. Thus, the role of causative factors in aetiology of cryptorchidism requires further research.

Exomic and Epigenomic Analyses in a Pair of Monozygotic Twins Discordant for Cryptorchidism

Cryptorchidism represents one of the most common human congenital anomalies. In most cases, its etiology remains unclear and seems to be multifactorial. In the present study, a pair of monozygotic twins discordant for cryptorchidism was identified. Twin zygosity was confirmed by microsatellite genotyping. Whole exome sequencing and methylated DNA immunoprecipitation sequencing (MeDIP-Seq) of DNA extract from leucocytes were performed to, respectively, evaluate their exomes and epigenomes. No differences in exome sequencing data were found between the twins after validation. MeDIP-Seq analysis detected 5,410 differentially hypermethylated genes and 2,383 differentially hypomethylated genes. Bioinformatic analysis showed that these genes belonged to several biological processes and signaling pathways, including regulation of actin cytoskeleton, which has been previously implicated in the etiology of cryptorchidism. The findings of the present study suggest that non-genetic factors might contribute to the pathogenesis of cryptorchidism.

Genomic copy number variation association study in Caucasian patients with nonsyndromic cryptorchidism

Background

Copy number variation (CNV) is a potential contributing factor to many genetic diseases. Here we investigated the potential association of CNV with nonsyndromic cryptorchidism, the most common male congenital genitourinary defect, in a Caucasian population.

Methods

Genome wide genotyping were performed in 559 cases and 1772 controls (Group 1) using Illumina HumanHap550 v1, HumanHap550 v3 or Human610-Quad platforms and in 353 cases and 1149 controls (Group 2) using the Illumina Human OmniExpress 12v1 or Human OmniExpress 12v1-1. Signal intensity data including log R ratio (LRR) and B allele frequency (BAF) for each single nucleotide polymorphism (SNP) were used for CNV detection using PennCNV software. After sample quality control, gene- and CNV-based association tests were performed using cleaned data from Group 1 (493 cases and 1586 controls) and Group 2 (307 cases and 1102 controls) using ParseCNV software. Meta-analysis was performed using gene-based test results as input to identify significant genes, and CNVs in or around significant genes were identified in CNV-based association test results. Called CNVs passing quality control and signal intensity visualization examination were considered for validation using TaqMan CNV assays and QuantStudio® 3D Digital PCR System.

Results

The meta-analysis identified 373 genome wide significant (p < 5X10⁻⁴) genes/loci including 49 genes/loci with deletions and 324 with duplications. Among them, 17 genes with deletion and 1 gene with duplication were identified in CNV-based association results in both Group 1 and Group 2. Only 2 genes (NUCB2 and UPF2) containing deletions passed CNV quality control in both groups and signal intensity visualization examination, but laboratory validation failed to verify these deletions.

Conclusions

Our data do not support that structural variation is a major cause of nonsyndromic cryptorchidism.

Electronic supplementary material

The online version of this article (doi:10.1186/s12894-016-0180-4) contains supplementary material, which is available to authorized users.

Mutational analysis of HOXA10 gene in Chinese patients with cryptorchidism

Cryptorchidism is one of the most common congenital anomalies and affects 2-4% of full-term new born boys. Its aetiology is poorly understood at present. HOXA10 plays a pivotal role in regulation of testicular descent. Male mice mutant for Hoxa10 exhibit unilateral or bilateral cryptorchidism as a result of impaired development of the gubernaculums. In this study, we performed mutation analysis of HOXA10 gene in a cohort of 98 cryptorchid patients. And we found a mutation (N27K) in a boy with unilateral cryptorchidism. The mutation was not detected in 106 healthy controls. Both in silico analyses and functional studies showed that the mutation affected the function of HOXA10. The results demonstrated that mutation in HOXA10 gene contributes to the pathogenesis of cryptorchidism, but may not be a common cause.

Pathway analysis supports association of nonsyndromic cryptorchidism with genetic loci linked to cytoskeleton-dependent functions

STUDY QUESTION

What are the genetic loci that increase susceptibility to nonsyndromic cryptorchidism, or undescended testis?

SUMMARY ANSWER

A genome-wide association study (GWAS) suggests that susceptibility to cryptorchidism is heterogeneous, with a subset of suggestive signals linked to cytoskeleton-dependent functions and syndromic forms of the disease.

WHAT IS KNOWN ALREADY

Population studies suggest moderate genetic risk of cryptorchidism and possible maternal and environmental contributions to risk. Previous candidate gene analyses have failed to identify a major associated locus, although variants in insulin-like 3 (INSL3), relaxin/insulin-like family peptide receptor 2 (RXFP2) and other hormonal pathway genes may increase risk in a small percentage of patients.

STUDY DESIGN, SIZE, DURATION

This is a case-control GWAS of 844 boys with nonsyndromic cryptorchidism and 2718 control subjects without syndromes or genital anomalies, all of European ancestry.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All boys with cryptorchidism were diagnosed and treated by a pediatric specialist. In the discovery phase, DNA was extracted from tissue or blood samples and genotyping performed using the Illumina HumanHap550 and Human610-Quad (Group 1) or OmniExpress (Group 2) platform. We imputed genotypes genome-wide, and combined single marker association results in meta-analyses for all cases and for secondary subphenotype analyses based on testis position, laterality and age, and defined genome-wide significance as P = 7 × 10(-9) to correct for multiple testing. Selected markers were genotyped in an independent replication group of European cases (n = 298) and controls (n = 324). We used several bioinformatics tools to analyze top (P < 10(-5)) and suggestive (P < 10(-3)) signals for significant enrichment of signaling pathways, cellular functions and custom gene lists after multiple testing correction.

MAIN RESULTS AND THE ROLE OF CHANCE

In the full analysis, we identified 20 top loci, none reaching genome-wide significance, but one passing this threshold in a subphenotype analysis of proximal testis position (rs55867206, near SH3PXD2B, odds ratio = 2.2 (95% confidence interval 1.7, 2.9), P = 2 × 10(-9)). An additional 127 top loci emerged in at least one secondary analysis, particularly of more severe phenotypes. Cytoskeleton-dependent molecular and cellular functions were prevalent in pathway analysis of suggestive signals, and may implicate loci encoding cytoskeletal proteins that participate in androgen receptor signaling. Genes linked to human syndromic cryptorchidism, including hypogonadotropic hypogonadism, and to hormone-responsive and/or differentially expressed genes in normal and cryptorchid rat gubernaculum, were also significantly overrepresented. No tested marker showed significant replication in an independent population. The results suggest heterogeneous, multilocus and potentially multifactorial susceptibility to nonsyndromic cryptorchidism.

LIMITATIONS, REASONS FOR CAUTION

The present study failed to identify genome-wide significant markers associated with cryptorchidism that could be replicated in an independent population, so further studies are required to define true positive signals among suggestive loci.

WIDER IMPLICATIONS OF THE FINDINGS

As the only GWAS to date of nonsyndromic cryptorchidism, these data will provide a basis for future efforts to understand genetic susceptibility to this common reproductive anomaly and the potential for additive risk from environmental exposures.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by R01HD060769 (the Eunice Kennedy Shriver National Institute for Child Health and Human Development (NICHD)), P20RR20173 (the National Center for Research Resources (NCRR), currently P20GM103464 from the National Institute of General Medical Sciences (NIGMS)), an Institute Development Fund to the Center for Applied Genomics at The Children's Hospital of Philadelphia, and Nemours Biomedical Research. The authors have no competing interests to declare.

Immunohistochemical expression of HOXA-13 in normal, hyperplastic and neoplastic canine prostatic tissue

Homeobox genes are known to be examples of the intimate relationship between embryogenesis and tumourigenesis. Specifically, the HOXA13 gene plays a fundamental role in the development of the urogenital tract and external genitalia and in prostate organogenesis. There are no reports on the expression of HOXA13 in normal, hyperplastic or neoplastic canine prostate tissue or in other types of tumours. Six normal, 16 hyperplastic and 12 neoplastic canine prostates were examined microscopically and immunohistochemically with a polyclonal antibody specific for human HOXA13. An immunohistochemical score was generated. HOXA13 was expressed in the cytoplasm of epithelial cells in normal, hyperplastic and neoplastic prostates. The percentage of immunolabelled cells in all prostatic carcinomas (PCs) was greatly increased, with a score of 85.3 (±5.25) compared with normal (2 ± 0.71) and hyperplastic prostates (6.08 ± 2.21). The increase in HOXA13 expression in canine PCs suggests the involvement of this transcription factor in carcinogenesis and promotion of tumour growth.

Pivotal role of the muscle-contraction pathway in cryptorchidism and evidence for genomic connections with cardiomyopathy pathways in RASopathies

BACKGROUND

Cryptorchidism is the most frequent congenital disorder in male children; however the genetic causes of cryptorchidism remain poorly investigated. Comparative integratomics combined with systems biology approach was employed to elucidate genetic factors and molecular pathways underlying testis descent.

METHODS

Literature mining was performed to collect genomic loci associated with cryptorchidism in seven mammalian species. Information regarding the collected candidate genes was stored in MySQL relational database. Genomic view of the loci was presented using Flash GViewer web tool (http://gmod.org/wiki/Flashgviewer/). DAVID Bioinformatics Resources 6.7 was used for pathway enrichment analysis. Cytoscape plug-in PiNGO 1.11 was employed for protein-network-based prediction of novel candidate genes. Relevant protein-protein interactions were confirmed and visualized using the STRING database (version 9.0).

RESULTS

The developed cryptorchidism gene atlas includes 217 candidate loci (genes, regions involved in chromosomal mutations, and copy number variations) identified at the genomic, transcriptomic, and proteomic level. Human orthologs of the collected candidate loci were presented using a genomic map viewer. The cryptorchidism gene atlas is freely available online: http://www.integratomics-time.com/cryptorchidism/. Pathway analysis suggested the presence of twelve enriched pathways associated with the list of 179 literature-derived candidate genes. Additionally, a list of 43 network-predicted novel candidate genes was significantly associated with four enriched pathways. Joint pathway analysis of the collected and predicted candidate genes revealed the pivotal importance of the muscle-contraction pathway in cryptorchidism and evidence for genomic associations with cardiomyopathy pathways in RASopathies.

CONCLUSIONS

The developed gene atlas represents an important resource for the scientific community researching genetics of cryptorchidism. The collected data will further facilitate development of novel genetic markers and could be of interest for functional studies in animals and human. The proposed network-based systems biology approach elucidates molecular mechanisms underlying co-presence of cryptorchidism and cardiomyopathy in RASopathies. Such approach could also aid in molecular explanation of co-presence of diverse and apparently unrelated clinical manifestations in other syndromes.

Testicular descent: INSL3, testosterone, genes and the intrauterine milieu

Complete testicular descent is a sign of, and a prerequisite for, normal testicular function in adult life. The process of testis descent is dependent on gubernacular growth and reorganization, which is regulated by the Leydig cell hormones insulin-like peptide 3 (INSL3) and testosterone. Investigation of the role of INSL3 and its receptor, relaxin-family peptide receptor 2 (RXFP2), has contributed substantially to our understanding of the hormonal control of testicular descent. Cryptorchidism is a common congenital malformation, which is seen in 2-9% of newborn boys, and confers an increased risk of infertility and testicular cancer in adulthood. Although some cases of isolated cryptorchidism in humans can be ascribed to known genetic defects, such as mutations in INSL3 or RXFP2, the cause of cryptorchidism remains unknown in most patients. Several animal and human studies are currently underway to test the hypothesis that in utero factors, including environmental and maternal lifestyle factors, may be involved in the etiology of cryptorchidism. Overall, the etiology of isolated cryptorchidism seems to be complex and multifactorial, involving both genetic and nongenetic components.

Cryptorchidism: pathogenesis, diagnosis, treatment and prognosis

Cryptorchidism is a common genital anomaly diagnosed at birth or during childhood. Genetic and/or environmental factors that alter expression or function of hormones crucial for testicular descent, insulin-like 3, and testosterone, may contribute to cryptorchidism. When identified at birth, surgical treatment is indicated by 6 months of age if testes fail to descend, or at the time of diagnosis in older children. A laparoscopic approach is preferred for abdominal testes. Early surgical therapy may reduce the risk of subfertility and/or malignancy.

Association of HOXA10, ZFPM2, and MMP2 genes with scrotal hernias evaluated via biological candidate gene analyses in pigs

OBJECTIVE

To evaluate the associations between 14 biological candidate genes and scrotal hernias in pigs.

ANIMALS

1,534 Pietrain-based pigs, including 692 individuals from 298 pig families and 842 male pigs without family information.

PROCEDURES

Pigs were classified as affected or unaffected for scrotal hernias. Single nucleotide polymorphisms of candidate genes were analyzed via PCR assays and genotyped. Statistical analyses were performed on the family-trio and the case-control data.

RESULTS

2 genes involved in collagen metabolism (homeobox A10 [HOXA10] and matrix metalloproteinases 2 [MMP2]) and 1 gene encoding zinc finger protein multitype 2 (ZFPM2, important in the development of diaphragmatic hernia) were significantly associated with hernias. Pigs with these genotypes had high odds of developing scrotal hernias in the case and control groups (2 ZFPM2 variants: odds ratio, 4.3 [95% confidence interval, 2.78 to 6.64] and 4.45[95%confidenceinterval,2.88to6.88]). Anothergene, collagentypeII A 1(COL2A1),was potentially involved in hernia development.

CONCLUSIONS AND CLINICAL RELEVANCE

HOXA10, ZFPM2, MMP2, and COL2A1 could have important roles in pig hernia development and potentially be useful for marker-assisted selection in the pig industry.

IMPACT FOR HUMAN MEDICINE

Pigs are used for the study of many human diseases because of their physiologic similarities. Genes associated with scrotal hernias in this study may be directly used in understanding the molecular mechanisms underlying this defect in humans.

Advances in molecular genetics of cryptorchidism

Cryptorchidism is the most common congenital disorder in boys; one major complication of this disorder is male infertility. Androgens are key hormones to complete testicular descent; therefore, impaired fetal androgen action can result in this anomaly; its molecular etiology, however, remains unknown. Recent molecular approaches might provide an opportunity to identify not only candidate genes but also several predictive markers of future fertility. The purpose of this review is to summarize the recent insight into the genetic pathway of testicular descent and the molecular etiology of isolated cryptorchidism, and discuss the prospects of treatment to achieve future fertility in such patients.

Undescended testis: current theories of etiology

PURPOSE OF REVIEW

Nonsyndromic cryptorchidism or undescended testis is a structural defect of infants and children whose etiology is unknown but likely related to a combination of genetic susceptibility and environmental factors. This review will focus on factors that may contribute to the etiology of this common and complex disease.

RECENT FINDINGS

The incidence of cryptorchidism is estimated to be 2-4% or higher in some populations. Data suggesting increasing prevalence are conflicting, possibly related to problems with diagnostic accuracy. Increased risk of cryptorchidism in first-degree relatives suggests a significant genetic contribution to susceptibility. Sequence variants within key candidate genes, such as insulin-like 3 and relaxin/insulin-like family peptide receptor 2, in cases of nonsyndromic cryptorchidism are infrequent and of unclear significance. Epidemiological data suggest that fetal growth restriction, maternal factors such as smoking, alcohol use and gestational diabetes, and exposure to environmental chemicals may contribute to risk, although data are inconsistent.

SUMMARY

The available evidence suggests a significant genetic contribution to cryptorchidism susceptibility that may be modulated by environmental risk factors. Additional studies are needed to define these factors, their complex interaction and their effects on testicular development and descent.

Role of hormones, genes, and environment in human cryptorchidism

Cryptorchidism is the most frequent congenital birth defect in male children (2-4% in full-term male births), and it has the potential to impact the health of the human male. In fact, although it is often considered a mild malformation, it represents the best-characterized risk factor for reduced fertility and testicular cancer. Furthermore, some reports have highlighted a significant increase in the prevalence of cryptorchidism over the last few decades. Etiology of cryptorchidism remains for the most part unknown, and cryptorchidism itself might be considered a complex disease. Major regulators of testicular descent from intraabdominal location into the bottom of the scrotum are the Leydig-cell-derived hormones testosterone and insulin-like factor 3. Research on possible genetic causes of cryptorchidism has increased recently. Abundant animal evidence supports a genetic cause, whereas the genetic contribution to human cryptorchidism is being elucidated only recently. Mutations in the gene for insulin-like factor 3 and its receptor and in the androgen receptor gene have been recognized as causes of cryptorchidism in some cases, but some chromosomal alterations, above all the Klinefelter syndrome, are also frequently involved. Environmental factors acting as endocrine disruptors of testicular descent might also contribute to the etiology of cryptorchidism and its increased incidence in recent years. Furthermore, polymorphisms in different genes have recently been investigated as contributing risk factors for cryptorchidism, alone or by influencing susceptibility to endocrine disruptors. Obviously, the interaction of environmental and genetic factors is fundamental, and many aspects have been clarified only recently.

HOXA10 mutations in congenital absence of uterus and vagina

OBJECTIVE

To analyze the HOXA10 genes in CAUV patients for mutations. Congenital absence of the uterus and vagina (CAUV) is the most extreme female reproductive tract developmental defect known. The HOXA10 gene is expressed in the developing and adult uterus. Female mice with loss-of-function Hoxa10 gene mutations have anteriorly directed homeotic transformations of the uterus. Because the HOXA10 gene is expressed in the embryonic paramesonephric (Müllerian) ducts, abnormally low expression by mutant HOXA10 genes might cause CAUV. This hypothesis was tested by analyzing the HOXA10 genes in CAUV patients for mutations.

DESIGN

Case-control study.

SETTING

Academic reproductive endocrinology and infertility practice.

PATIENT(S)

Blood samples were obtained from 26 patients with CAUV and 30 normal controls.

INTERVENTION(S)

DNA samples prepared from blood leukocytes were used as templates for polymerase chain reaction (PCR) amplification of DNA fragments from the HOXA10 gene. The gene fragments were tested for DNA sequence differences using denaturing gradient gel electrophoresis (DGGE).

MAIN OUTCOME MEASURE(S)

To detect DNA sequence differences between patients with CAUV and normal controls.

RESULT(S)

No DNA sequence differences were found in either patients with CAUV or normal controls in either of the two protein-coding exons of the HOXA10 gene.

CONCLUSION(S)

Because no HOXA10 gene mutations were found in 26 patients from 25 unrelated families, germ- line mutations in the HOXA10 gene are not a common cause of CAUV.

Hormonal and genetic control of testicular descent

Cryptorchidism has the potential to affect the health of the human male. Although it is often considered a mild malformation, it represents the best-characterized risk factor for reduced fertility and testicular cancer. The aetiology of cryptorchidism remains, for the most part, unknown and cryptorchidism itself might be considered a complex disease. This reflects the intricate mechanisms regulating testicular development and descent from intra-abdominal location into the bottom of the scrotum, involving different anatomical and hormonal factors. Major actors of testicular descent are the Leydig cell-derived hormones testosterone and insulin-like factor 3, even if other factors may play a role. Although considerable evidence exists in animals to support a genetic cause, the genetic contribution to human cryptorchidism is only recently being elucidated. Environmental factors might also contribute to the aetiology of cryptorchidism and its increased incidence in recent years. Mutations in the gene for insulin-like factor 3 and its receptor and in the androgen receptor gene explain a minority of cases of cryptorchidism, but research on genetic polymorphisms that may also influence susceptibility to endocrine disruptors is shedding light on this field.

Signalling molecules: clues from development of the limb bud for cryptorchidism?

Recent studies of testicular descent suggest not only that the gubernaculum does not initially attach to the scrotum, but also that it must migrate from the groin. Two findings suggest that the gubernaculum may behave like an embryonic limb bud during this phase. First, the active growth centre is at the distal tip of the gubernaculum. Secondly, the gubernaculum is loose in the subcutaneous tissues beneath Scarpa's fascia. The free protrusion of the gubernaculum from the abdominal wall was so reminiscent of a developing embryonic limb bud, we thought that the biological controls of both processus may be similar. This review examines what is known about vertebrate limb bud development, and compares the mechanisms to what has recently been discovered in the gubernaculum. The hypothesis that both processes may be similar is initially consistent with the current facts, encouraging us to investigate this further experimentally.

Allelic variants inHOX genes in cryptorchidism

BACKGROUND

Cryptorchidism is one of the most common congenital anomalies and is associated with increased risk for infertility and testicular cancer later in life. Findings from animal models and small clinical studies suggest that the posterior HOX genes (paralogs 9-13) could be potential candidate genes for cryptorchidism and that the HOX genes are functionally redundant within paralogous groups.

METHODS

The coding regions and exon-intron boundaries of the 16 posterior HOX genes were sequenced and analyzed in group 1 (44 nonsyndromic cryptorchidism cases and 46 healthy controls). Those specific variants found to be significantly different between cases and controls in group 1 were examined in DNA from group 2 (108 cases and 114 controls).

RESULTS

A total of 57 variants was found in group 1, among which the allele frequency of 180A>G (A60A) in HOXD13 alone was significantly elevated in cases versus controls (P = 0.02). In the combined 1 + 2 group, cases were also more likely than controls to have the G allele (P = 0.002). As predicted by an exonic splicing enhancer finder program, the 180A>G (A60A) variant is expected to have an influence on the splicing of transcripts from HOXD13. In group 1, case subjects were more likely to carry multiple variants in HOXA13 and HOXD13 (P = 0.02) than controls.

CONCLUSIONS

The variant 180A>G (A60A) in HOXD13 is a risk factor for cryptorchidism, and a dynamic equilibrium of genes in HOX paralog 13 is involved in the pathogenesis of cryptorchidism.

Endocrine regulation of HOX genes

Hox genes have a well-characterized role in embryonic development, where they determine identity along the anteroposterior body axis. Hox genes are expressed not only during embryogenesis but also in the adult, where they are necessary for functional differentiation. Despite the known function of these genes as transcription factors, few regulatory mechanisms that drive Hox expression are known. Recently, several hormones and their cognate receptors have been shown to regulate Hox gene expression and thereby mediate development in the embryo as well as functional differentiation in the adult organism. Estradiol, progesterone, testosterone, retinoic acid, and vitamin D have been shown to regulate Hox gene expression. In the embryo, the endocrine system directs axial Hox gene expression; aberrant Hox gene expression due to exposure to endocrine disruptors contributes to the teratogenicity of these compounds. In the adult, endocrine regulation of Hox genes is necessary to enable such diverse functions as hematopoiesis and reproduction; endocrinopathies can result in dysregulated HOX gene expression affecting physiology. By regulating HOX genes, hormonal signals utilize a conserved mechanism that allows generation of structural and functional diversity in both developing and adult tissues. This review discusses endocrine Hox regulation and its impact on physiology and human pathology.

Disrupted sex differentiation and feminization of man and domestic animals

Genital malformations constitute the most common birth defects in man and domestic animals and occur frequently in males since the participation of many genes is required for sex differentiation to proceed in the male direction. The precise dose, timing, and coordination needed for their expression add to the proneness of various stages in male sex differentiation to external influences. The emerging insight, through the identification of genes involved in the sex differentiation cascade, is that over 85% of sex anomalies in human and domestic animal populations are not attributable to chromosome aberrations or to mutations in a known gene. Since a majority of severely malformed individuals are incapable of reproduction, the high rates of these defects have to be results either of new mutations or of collaboration of environmental factors with genes. Increase in specific malformations in domestic animals often indicates increased concentration of liability genes brought together in the conceptus by inbreeding. However, in human populations where inbreeding is not the norm such increases may reflect environment-induced new mutations or interaction of environmental agents with hormone-sensitive genes. This review summarizes the information currently available on the genetics of major events in male sex differentiation and briefly discusses the collaborative role that environment may play in disrupting different components of this process.

Cryptorchidism: an indicator of testicular dysgenesis?

Cryptorchidism is a common ailment of new-born boys, affecting 1-9% of full term boys at birth. Cryptorchidism has been associated with an increased risk of testicular cancer and reduced fertility. Aetiology of cryptorchidism remains obscure in most cases. Familial occurrence suggests a heritable susceptibility to cryptorchidism; however, seasonal variation in the incidence of cryptorchidism suggests that environmental factors also contribute. Testicular descent is characterised by androgen-dependent regression of cranial suspensory ligament and androgen + insulin-like hormone 3 (Ins l3)-dependent gubernacular outgrowth. Even though hormonal defects are rarely detected in patients, both hypo-and hypergonadotropic hormonal patterns have been associated with cryptorchidism. Moreover, cryptorchid boys have significantly reduced serum androgen bioactivity at 3 months of age when normal boys have a strong surge of reproductive hormones. Defects in Ins l3 action cause cryptorchidism in male mice, and over-expression in female mice causes ovarian descent. Defects in leucine-rich repeat-containing G-protein-coupled receptor 8/G-protein-coupled receptor affecting testis descent (LGR8/GREAT), the receptor for Ins l3, manifest the same phenotype as Ins l3 knockout mutants. Even though mutations found in Ins l3 and LGR8/GREAT genes are not a common cause of cryptorchidism in patients, it remains to be resolved whether low Ins l3 levels during development are associated with cryptorchidism. Cryptorchidism may reflect foetal testicular dysgenesis that may later manifest as subfertility or testicular cancer.

Folate modulates Hox gene-controlled skeletal phenotypes

Hox genes are well-known regulators of pattern formation and cell differentiation in the developing vertebrate skeleton. Although skeletal variations are not uncommon in humans few mutations in human HOX genes have been described. If such mutations are compatible with life, there may be physiological modifiers for the manifestation of Hox gene-controlled phenotypes, masking underlying mutations. Here we present evidence that the essential nutrient folate modulates genetically induced skeletal defects in Hoxd4 transgenic mice. We also show that chondrocytes require folate for growth and differentiation and that they express folate transport genes, providing evidence for a direct effect of folate on skeletal cells. To our knowledge, this is the first report of nutritional influence on Hox gene-controlled phenotypes, and implicates gene-environment interactions as important modifiers of Hox gene function. Taken together, our results demonstrate a beneficial effect of folate on skeletal development that may also be relevant to disorders and variations of the human skeleton.

Idiopathic impaired spermatogenesis: genetic epidemiology is unlikely to provide a short-cut to better understanding

The aetiology of impaired spermatogenesis is unknown in the majority of subfertile men. From several studies of concordance for involuntary childlessness among men, we can conclude that there is a substantial familial component in male subfertility and that shared loci segregating through families can be assumed. We now know that deletions on the Y chromosome, which do not penetrate fully, account for some of these cases. There are good reasons to suspect that other cases result from mutations in genes located elsewhere in the genome. In this article, we discuss different approaches to unravelling the molecular basis of impaired spermatogenesis originating from genetic abnormalities in chromosomes other than the Y chromosome. Genetic mapping studies are in general a good approach to detect disease-causing genes that are segregating through a population; they can provide a shortcut to unravelling the biochemistry of a disease. In this paper, we explain our reasons for arguing that linkage and association studies are no promising means to identify the genes causing impaired spermatogenesis. We conclude that direct screening of candidate genes for mutations will be necessary to detect genes involved in impaired spermatogenesis. However, this approach requires studies of the biochemical pathways of normal and abnormal spermatogenesis. Since we have a poor understanding of these pathways, more research is needed into the biochemistry of spermatogenesis.

Cryptorchidism: diagnosis, treatment, and long-term prognosis

Cryptorchidism is a common anomaly treated by every pediatric urologist. The etiology is multifactorial and includes hormonal and molecular factors. Diagnostic abilities may be enhanced by radiologic advances. Hormonal and surgical treatment modalities are discussed herein, as well as the identification and prevention of long-term sequelae.

Lack of LGR8 gene mutation in Finnish patients with a family history of cryptorchidism

Cryptorchidism is the most frequent congenital anomaly of the urogenital tract in the male. Although in Western countries 1-2% of males at the age of 3 months are diagnosed with this condition, its aetiology is still unknown. Animal models suggest a possible genetic basis for this disorder. Recently, the INSL3 (Leydig insulin-like peptide) gene and its cognate receptor, LGR8, were found to be important in testicular descent by regulating gubernacular development. Male mice null for either INSL3 or LGR8 genes exhibited bilateral cryptorchidism. Because earlier studies indicated that mutation of the INSL3 gene is not associated with the development of human cryptorchidism, this study analysed whether mutations in the LGR8 gene could be associated with this disorder. Sequencing of 18 exons of the LGR8 gene in 23 cryptorchid Finnish patients and a group of 33 control subjects allowed the identification of three nucleotide changes in exons 12 and 17, showing single base substitutions from A to G at positions 957, 993, and 1810 of LGR8. Among the three changes, only the 1810 A to G substitution is associated with an amino acid change from isoleucine to valine (Ile604Val) located in the fifth transmembrane domain of this seven-transmembrane receptor. This change was more frequent in a control group of normal fertile adult males and infant boys than in the group of cryptorchid males. The change is not associated with altered receptor signalling, thus suggesting the presence of a polymorphism unrelated to the cryptorchid phenotype. These data indicate that mutations involving the human LGR8 gene do not represent a frequent cause of cryptorchidism in the Finnish population.

Absence of Y chromosome microdeletions in patients with cryptorchidism and hypospadias

Microdeletions of the Y chromosome have been observed in some patients with cryptorchidism and severe defects of spermatogenesis. We investigated whether microdeletions of the Y chromosome may be present in patients with cryptorchidism and hypospadias. Peripheral blood was obtained from 20 male patients 5.8 +/- 4.1 years (range: 0.4-14 years) with cryptorchidism and hypospadias for somatic DNA analysis of Y chromosome using multiplex polymerase chain reaction. These patients had no identifiable genetic syndrome, other genitourinary malformations or an abnormal karyotype. We evaluated the presence or absence of amplification using a set of 34 different sequence-tagged sites (STS) in each patient. All patients showed normal length amplifications for each of the regions evaluated, suggesting that microdeletions of the Y chromosome are not a frequent cause of hypospadias associated with cryptorchidism.

Homeobox HOXA10 gene analysis in cryptorchidism

BACKGROUND

In male mice, targeted disruption of the homeobox gene hoxa10 causes cryptorchidism and infertility. Genetic alterations in exon 1 of HOXA10 have been found in a high number of boys with cryptorchidism.

AIM

To evaluate whether mutations of HOXA10 can be a common cause of cryptorchidism.

PATIENTS AND METHODS

Genomic DNA was extracted from 18 patients with cryptorchidism (age 7-44 years; unilateral n = 13; no familial cases) and 28 healthy controls (age 9-39 years). HOXA10 was amplified by PCR and all coding sequences of exon 1 and 2 were sequenced. The PCR products were digested by ScrFI restriction enzyme and the restriction fragments obtained were analyzed on 2% agarose gel.

RESULTS

One silent polymorphism, G-->A substitution at position 1203, was detected in 2/18 patients (11.1%). The same polymorphism was detected in 3/28 controls (10.7%).

CONCLUSIONS

These data on HOXA10 analysis indicate that alterations of this gene may be more rare in males with cryptorchidism than previously suggested. This finding agrees with the rare occurrence of INSL3 gene mutations in human cryptorchidism, but needs to be confirmed in a larger series of selected patients.

Update on cryptorchidism: endocrine, environmental and therapeutic aspects

Cryptorchidism is the most frequent developmental abnormality in boys, present in more than 1% of infants above three months of age. It is associated with an increased risk of infertility and testicular cancer. The etiological quest is often disappointing, except in bilateral cases or associated malformations. Recent focus is on genetic and environmental aspects. Animal models have revealed the role of genes encoding for proteins implicated in testicular migration (InsI3, Hoxa 10), but in humans results are less convincing. While some degree of endogenous hormonal abnormality is suspeeted in some patients, the endocrine disruptor hypothesis is also tested. It is unclear whether the incidence of cryptorchidism has really increased, or whether there is only a better screening for this condition. However, other male reproductive problems, such as subfertility, hypospadias and testicular cancer seem on the rise. This secular trend suggests the possible in utero impact of hormonally active environmental factors, such as pesticides with estrogenic or antiandrogenic effect, and is consistent with the increased risk of cryptorchidism observed in the sons of mothers exposed to diethylstilbestrol during pregnancy. From a therapeutic point of view, there is an agreement that the correction of cryptorchidism is needed, but there is controversy on the best medical and/or surgical approach and on the optimal timing. There is a recent trend in proposing early therapeutic intervention, before 1 yr of age, in the hope of improving fertility; however, there is no proof that such a strategy can reduce the risk of testicular cancer.

Cryptorchidism: seasonal variations in Greece do not support the theory of light

To examine seasonal trends of cryptorchidism in Greece, 583 males with true isolated cryptorchidism were analyzed. All 208 912 live-born boys born during the same period were used as a comparison group. Seasonality by month of birth was evaluated using both Edwards' model with adjusted frequencies and exact theta(i), and Walter-Elwood method with exact theta(i). Both tests resulted in consistent findings. The incidence of cryptorchid births in Greece follows a documented cyclic pattern of simple harmonic type with spring being the season of statistical predominance (peak in March with a second, almost equivalent, peak in May). In contrast, in autumn the incidence of cryptorchid births was considerably lower (trough in September). Given the fact that no significant differences in daylight length are found among seasons in Greece, the detection of a significant seasonal variation suggests that factors other than light are involved in the pathogenesis of cryptorchidism. Low environmental temperature is proposed as a causative factor negatively influencing the maternal hCG profiles and the inguinoscrotal phase of testicular descent. This is further supported by: (i) the similarity of our results to those reported by other European countries of different longitude and geographical width and (ii) our data showing significantly smaller maternal hCG profiles at the 26th week of gestation during winter compared with summer.

Absence of mutations in the HoxA10, HoxA11 and HoxD11 nucleotide coding sequences in thrombocytopenia with absent radius syndrome

Recent studies have suggested the HoxA10, HoxA11 and HoxD11 homeobox genes as candidate loci for the thrombocytopenia with absent radius (TAR) syndrome. For example, targeted disruptions of these Hox genes result in abnormal development of the mouse radius, while overexpression of HoxA10 stimulates mouse megakaryocyte (MK) development in vitro. To examine the expression of Hox genes in human MK cells, we utilized reverse transcription polymerase chain reaction with degenerate oligonucleotides to study megakaryocytic cell lines (MEG-01, DAMI), and primary human MK purified from adult and cord blood. Using this approach, 13 out of 40 clones isolated from cell lines, 10 out of 21 from cord MK, and 11 out of 21 from adult MK were identified as HoxA10, while HoxA11 and HoxD11 sequences were not detected. The normal genomic sequences for the human HoxA10, -A11, and -D11 genes were then determined and sequenced in 10 unrelated individuals with TAR syndrome. In all patients the derived amino acid sequence for the three Hox genes was identical to normal controls. Southern blotting did not reveal genomic rearrangements or deletions at these loci, and in two patients intact HoxA10 transcripts were detected by amplification in myeloid cells. Although these studies cannot completely exclude the possibility that the TAR syndrome results from non-coding mutations that affect the level of Hox gene expression in megakaryocytes, mutations in the coding sequence of the Hox genes known to affect radial development are not a common cause of TAR syndrome.

Complete mutation analysis panel of the 39 human HOX genes

BACKGROUND

The HOX gene family consists of highly conserved transcription factors that specify the identity of the body segments along the anteroposterior axis of the embryo. Because the phenotypes of mice with targeted disruptions of Hox genes resemble some patterns of human malformations, mutations in HOX genes have been expected to be associated with a significant number of human malformations. Thus far, however, mutations have been documented in only three of the 39 human HOX genes (HOXD13, HOXA13, and HOXA11) partly because current knowledge on the complete coding sequence and genome structure is limited to only 20 of the 39 human HOX genes.

METHODS

Taking advantage of the human and mouse draft genome sequences, we attempted to characterize the remaining 19 human HOX genes by bioinformatic analysis including phylogenetic footprinting, the probabilistic prediction method, and comparison of genomic sequences with the complete set of the human anonymous cDNA sequences.

RESULTS

We were able to determine the full coding sequences of 19 HOX genes and their genome structure and successfully designed a complete set of PCR primers to amplify the entire coding region of each of the 39 HOX genes from genomic DNA.

CONCLUSIONS

Our results indicate the usefulness of bioinformatic analysis of the draft genome sequences for clinically oriented research projects. It is hoped that the mutation panel provided here will serve as a launchpad for a new discourse on the genetic basis of human malformations.

Different insulin-like 3 (INSL3) gene mutations not associated with human cryptorchidism

Cryptorchidism is the most frequent congenital anomaly of the urogenital tract in the male, but its etiology is for the most part unknown. Evidence suggests that a possible genetic cause may be involved. Animal models support this hypothesis, and in particular INSL3 (Leydig insulin-like 3 hormone) has been proposed as putative gene for cryptorchidism, since male mice mutant for Insl3 exhibit bilateral abdominal cryptorchidism due to alteration of gubernaculum development. In this study, we analyzed whether mutations in INSL3 could be associated with human cryptorchidism. Heteroduplex analysis and sequencing of both exons of INSL3 in 65 ex-cryptorchid patients and a group of control subjects allowed us to find four nucleotide changes in the sequence of exon I. These mutations are all single base substitutions from G to A at position 27, 96, 126 and 178. Only the 178G-->A substitution changes codon 60 from alanine to threonine (A60T). All mutations were found in comparable distribution in ex-cryptorchid patients and non-cryptorchid men. Therefore, all mutations represent neutral polymorphisms not associated with phenotype. This study confirms previous observations and demonstrates a novel polymorphism in the INSL3 gene. In contrast to that described for the mutant mouse, these data indicate that mutations of INSL3 do not seem to represent a frequent cause of cryptorchidism.

Human HOX gene mutations

HOX genes play a fundamental role in the development of the vertebrate central nervous system, axial skeleton, limbs, gut, urogenital tract and external genitalia, but it is only in the last 4 years that mutations in two of the 39 human HOX genes have been shown to cause congenital malformations; HOXD13, which is mutated in synpolydactyly, and HOXA13, which is mutated in Hand-Foot-Genital syndrome. Here we review the mutations already identified in these two genes, consider how these mutations may act, and discuss the possibility that further mutations remain to be discovered both in developmental disorders and in cancer.

Insulin-like 3/relaxin-like factor gene mutations are associated with cryptorchidism

Cryptorchidism is a common anomaly of male sexual differentiation. Two phases of testicular descent are recognized, transabdominal and inguinoscrotal. With evidence that androgens and Müllerian inhibitory hormone were not completely responsible for testicular descent, the existence of a third testicular hormone mediating testicular descent was postulated. Insulin-like 3 (INSL3) [also known as relaxin-like factor (RLF) and Leydig insulin-like protein (LEY I-L)] is a member of the insulin/relaxin hormone superfamily that is highly expressed in Leydig cells. The phenotype of transgenic mice with targeted deletion of the Insl3 gene was bilateral cryptorchidism with morphological evidence of abnormal gubernacular development. With this implicit evidence that Insl3 mediates testicular descent in mice, we performed mutation detection analysis of the coding regions of the 2 exon INSL3 gene in genomic DNA samples obtained from 145 formerly cryptorchid patients and 36 adult male controls. Single-strand conformational polymorphism analysis was used for the mutation detection studies. Two mutations, R49X and P69L, and several polymorphisms were identified. Both mutations were located in the connecting peptide region of the protein. The frequency of INSL3/RLF gene mutations as a cause of cryptorchidism is low, because only 2 of 145 (1.4%) formerly cryptorchid patients were found to have mutations.

A common polymorphism in the human relaxin-like factor (RLF) gene: no relationship with cryptorchidism

The incidence of impaired testicular descent (cryptorchidism) is high; 1-2% of boys at the age of 3 mo are diagnosed for this condition in western countries. Recent data on mice with targeted disruption of the Insl3/relaxin-like factor (RLF) gene proposed that this factor plays a role in testicular descent in fetal life. Male RLF-/- mice exhibit bilateral cryptorchidism due to developmental abnormalities of the gubernaculum, associated with abnormal spermatogenesis and infertility. In the present study, we have sequenced the promoter region and both exons of the RLF gene in a cohort of 30 boys, seven of whom presented with a possible familial form of cryptorchidism and 23 with sporadic cryptorchidism. One of the nucleotide substitutions detected, G to A at position 178, predicted amino acid change. The mutation was localized to the C-peptide region, resulting in an alanine to threonine change and therefore classified as a conservative mutation. Four of the 30 cases analyzed were homozygous (13%), and 15 were heterozygous for the mutation (50%). However, the same mutation was also found in a control group of 89 men; 10% of them were homozygous, and 39% were heterozygous. Our results indicate that mutations in the RLF gene are not a common reason for cryptorchidism and that the common G178A polymorphism has no apparent relationship with this condition.