Investigation of KIT gene mutations in women with 46,XX spontaneous premature ovarian failure

Pathways Involved in Premature Ovarian Failure: A Systematic Review of Experimental Studies

Premature ovarian failure (POF), which may be undetectable for a long time, is associated with impaired fertility. The mechanisms involved in the pathogenesis of POF as well as the concomitant treatments are still unclear. Although many data exist, mainly produced by the study of transgenic animals under various experimental conditions, they remain fragmented. A systematic review of the pathways involved in premature ovarian failure was conducted. Data extraction was performed from experimental studies until 2019. The molecular processes and their correlation with the follicular developmental stage have been described. Furthermore, the effects in other cells, such as oocytes, granulosa and theca cells have been reported. An overall estimation was conducted.

Basonuclin 1 deficiency is a cause of primary ovarian insufficiency

Primary ovarian insufficiency (POI) leads to infertility and premature menopause in young women. The genetic etiology of this disorder remains unknown in most patients. Using whole exome sequencing of a large Chinese POI pedigree, we identified a heterozygous 5 bp deletion inducing a frameshift in BNC1, which is predicted to result in a non-sense-mediated decay or a truncated BNC1 protein. Sanger sequencing identified another BNC1 missense mutation in 4 of 82 idiopathic patients with POI, and the mutation was absent in 332 healthy controls. Transfection of recombinant plasmids with the frameshift mutant and separately with the missense mutant in HEK293T cells led to abnormal nuclear localization. Knockdown of BNC1 was found to reduce BMP15 and p-AKT levels and to inhibit meiosis in oocytes. A female mouse model of the human Bnc1 frameshift mutation exhibited infertility, significantly increased serum follicle-stimulating hormone, decreased ovary size and reduced follicle numbers, consistent with POI. We report haploinsufficiency of BNC1 as an etiology of human autosomal dominant POI.

The Role of Gene Therapy in Premature Ovarian Insufficiency Management

Premature ovarian insufficiency (POI) is a highly prevalent disorder, characterized by the development of menopause before the age of 40. Most cases are idiopathic; however, in some women the cause of this condition (e.g.; anticancer treatment, genetic disorders, and enzymatic defects) could be identified. Although hormone-replacement therapy, the principal therapeutic approach for POI, helps alleviate the related symptoms, this does not effectively solve the issue of fertility. Assisted reproductive techniques also lack efficacy in these women. Thus, an effective approach to manage patients with POI is highly warranted. Several mechanisms associated with POI have been identified, including the lack of function of the follicle-stimulating hormone (FSH) receptor, alterations in apoptosis control, mutations in Sal-like 4 genes, and thymulin or basonuclin-1 deficiency. The above mentioned may be good targets for gene therapy in order to correct defects leading to POI. The goal of this review is to summarize current experiences on POI studies that employed gene therapy, and to discuss possible future directions in this field.

Genetics of female infertility due to anomalies of the ovary and mullerian ducts

Genetic factors are pivotal in reproductive development and subsequent reproductive processes. If disturbed, infertility can occur. In the female, genetic factors affecting the ovary and the uterus are not uncommon causes of infertility. Terminal deletions on the X long arm and X short arm and X chromosomal mosaicism have long been accepted as causes of premature ovarian failure (POF). Responsible genes on the X have not yet elucidated. Attractive candidate genes for POF also exist on autosomes, and in over a dozen genes molecular perturbations are documented in non-syndromic POF. The most common single-gene cause of POF is premutation carriers for FMR1 (fragile X syndrome). As other candidate genes and additional ethnic groups are interrogated, the proportion of POF cases due to single-gene mutation will increase. Among uterine anomalies, incomplete mullerian fusion is most common. Increased recurrence risks for first-degree relatives confirm a role for genetic factors; interrogation of candidate genes is under way.

The overexpression of KIT proto-oncogene in acute leukemic cells is not necessarily caused by the gene mutation

KIT is detected in a variety of cells, also in acute leukemia. Inhibition of wild-type KIT is not always satisfactory. The aim of this work was to evaluate the frequency of the most common KIT mutations in acute myeloid leukemia (AML) and determine the correlation between mutation and expression level. Samples were obtained from 75 patients with AL. CD117 presence was shown in 45 of 51 patients with AML and in 1 of 16 patients with acute lymphocytic leukemia (ALL). Asp816Val mutation was found in 3.5% of cases of AML and Val560Gly mutation in 1 sample with acute biclonal leukemia. Other genetic changes were found in 15 of 57 samples with AML: polymorphisms Met541Leu in 14% of cases, Lys546Lys in 7% and 1 case of acute biclonal leukemia, Ile798Ile in 5.3% of cases, Met541Leu in 1 acute biphenotypic leukemia and in 6.3% of ALL. Polymorphism Lys546Lys was also shown in 1 case of acute biclonal leukemia. Nonsilent genetic changes were detected in a total of 23% cases with core binding factor leukemia. There was no statistical significance between KIT expression and genetic changes. There was no correlation between the incidence and types of KIT mutations and its expression on cells in AML.

The role of humans in facilitating and sustaining coat colour variation in domestic animals

Though the process of domestication results in a wide variety of novel phenotypic and behavioural traits, coat colour variation is one of the few characteristics that distinguishes all domestic animals from their wild progenitors. A number of recent reviews have discussed and synthesised the hundreds of genes known to underlie specific coat colour patterns in a wide range of domestic animals. This review expands upon those studies by asking how what is known about the causative mutations associated with variable coat colours, can be used to address three specific questions related to the appearance of non wild-type coat colours in domestic animals. Firstly, is it possible that coat colour variation resulted as a by-product of an initial selection for tameness during the early phases of domestication? Secondly, how soon after the process began did domestic animals display coat colour variation? Lastly, what evidence is there that intentional human selection, rather than drift, is primarily responsible for the wide range of modern coat colours? By considering the presence and absence of coat colour genes within the context of the different pathways animals travelled from wild to captive populations, we conclude that coat colour variability was probably not a pleiotropic effect of the selection for tameness, that coat colours most likely appeared very soon after the domestication process began, and that humans have been actively selecting for colour novelty and thus allowing for the proliferation of new mutations in coat colour genes.

Colours of domestication

During the last decade, coat colouration in mammals has been investigated in numerous studies. Most of these studies addressing the genetics of coat colouration were on domesticated animals. In contrast to their wild ancestors, domesticated species are often characterized by a huge allelic variability of coat-colour-associated genes. This variability results from artificial selection accepting negative pleiotropic effects linked with certain coat-colour variants. Recent studies demonstrate that this selection for coat-colour phenotypes started at the beginning of domestication. Although to date more than 300 genetic loci and more than 150 identified coat-colour-associated genes have been discovered, which influence pigmentation in various ways, the genetic pathways influencing coat colouration are still only poorly described. On the one hand, similar coat colourations observed in different species can be the product of a few conserved genes. On the other hand, different genes can be responsible for highly similar coat colourations in different individuals of a species or in different species. Therefore, any phenotypic classification of coat colouration blurs underlying differences in the genetic basis of colour variants. In this review we focus on (i) the underlying causes that have resulted in the observed increase of colour variation in domesticated animals compared to their wild ancestors, and (ii) the current state of knowledge with regard to the molecular mechanisms of colouration, with a special emphasis on when and where the different coat-colour-associated genes act.

Association of paediatric mastocytosis with a polymorphism resulting in an amino acid substitution (M541L) in the transmembrane domain of c-KIT

BACKGROUND

The receptor tyrosine kinase c-KIT plays a key role in normal mast cell development. Point mutations in c-KIT have been associated with sporadic or familial mastocytosis.

OBJECTIVES

Two unrelated pairs of apparently identical twins affected by cutaneous mastocytosis attending the Mastocytosis Clinic at the Royal Children's Hospital, Melbourne, provided an opportunity to assess the possible contribution of c-KIT germline mutations or polymorphisms in this disease.

METHODS

Tissue biopsy, blood and/or buccal swab specimens were collected from 10 children with mastocytosis. To detect germline mutations/polymorphisms in c-KIT, we studied all coding exons by denaturing high pressure liquid chromatography. Exons showing mismatches were examined by direct sequencing. The influence of the substitution identified was further examined by expressing the variant form of c-KIT in factor-dependent FDC-P1 cells.

RESULTS

In both pairs of twins, a heterozygous ATG to CTG transition in codon 541 was observed, resulting in the substitution of a methionine residue in the transmembrane domain by leucine (M541L). In each case, one parent was also heterozygous for this allele. Expression of M541L KIT in FDC-P1 cells enabled them to grow in human KIT ligand (stem cell factor, SCF) but did not confer factor independence. Compared with cells expressing wild-type KIT at a similar level, M541L KIT-expressing cells displayed enhanced growth at low levels of SCF, and heightened sensitivity to the KIT inhibitor, imatinib mesylate.

CONCLUSIONS

The data suggest that the single nucleotide polymorphism resulting in the substitution M541L may predispose to paediatric mastocytosis.

Genetic investigation of four meiotic genes in women with premature ovarian failure

OBJECTIVE

The goal of this study was to determine whether mutations of meiotic genes, such as disrupted meiotic cDNA (DMC1), MutS homolog (MSH4), MSH5, and S. cerevisiae homolog (SPO11), were associated with premature ovarian failure (POF).

DESIGN

Case-control study.

METHODS

Blood sampling, karyotype, hormonal dosage, ultrasound, and ovarian biopsy were carried out on most patients. However, the main outcome measure was the sequencing of genomic DNA from peripheral blood samples of 41 women with POF and 36 fertile women (controls).

RESULTS

A single heterozygous missense mutation, substitution of a cytosine residue with thymidine in exon 2 of MSH5, was found in two Caucasian women in whom POF developed at 18 and 36 years of age. This mutation resulted in replacement of a non-polar amino acid (proline) with a polar amino acid (serine) at position 29 (P29S). Neither 36 control women nor 39 other patients with POF possessed this genetic perturbation. Another POF patient of African origin showed a homozygous nucleotide change in the tenth of DMC1 gene that led to an alteration of the amino acid composition of the protein (M200V).

CONCLUSIONS

The symptoms of infertility observed in the DMC1 homozygote mutation carrier and in both patients with a heterozygous substitution in exon 2 of the MSH5 gene provide indirect evidence of the role of genes involved in meiotic recombination in the regulation of ovarian function. MSH5 and DMC1 mutations may be one explanation for POF, albeit uncommon.

Novel missense mutations of the Deleted-in-AZoospermia-Like (DAZL) gene in infertile women and men

BACKGROUND

The Deleted-in-AZoospermia-Like (DAZL) gene has homologs required for germ cell development in many organisms. Recently, we showed that there are several common polymorphisms within the DAZL gene that are associated with age at ovarian failure/menopause and sperm count.

METHODS

Here we sought to identify rare mutations in DAZL and examine their phenotypes in men and women. We sequenced the DAZL gene in 519 individuals; sequences spanned the entire coding region of the gene.

RESULTS

We report the identification of four putative missense mutations in DAZL. Three individuals that were heterozygous for a DAZL mutation reported having children, while two individuals that were homozygous reported no children. These mutations were found only in infertile men and women.

CONCLUSION

Given the strong data associating DAZL polymorphisms and deletions with fertility in humans and model organisms, we suggest that these mutations may be associated with age at menopause and/or sperm count and warrant further biochemical and genetic investigation.

Investigation of the human stem cell factor KIT ligand gene, KITLG, in women with 46,XX spontaneous premature ovarian failure

OBJECTIVE

To investigate mutations in the human KIT ligand gene (KITLG) gene as a mechanism of 46,XX spontaneous premature ovarian failure. The human KIT ligand gene, known also as human stem cell factor, is the ligand of the c-kit transmembrane tyrosine kinase receptor (KIT). This ligand-receptor interaction is known to play important roles in mouse germ cell migration and proliferation.

DESIGN

Cross-sectional study.

SETTING

Clinical research center.

PATIENT(S)

Forty women with 46,XX spontaneous premature ovarian failure.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Single-stranded conformational polymorphism analysis and DNA sequencing.

RESULT(S)

We found one nucleotide change of the KITLG coding region (811G-->T) that led to an alteration of the amino acid composition of the KITLG protein in one Caucasian patient (Asp210Tyr). However, we found the same alteration in two normal control Caucasian samples. Three nucleotide substitutions were found in the noncoding exon of KITLG (exon 10). We also identified two intronic polymorphisms. Thus, we did not identify a single significant mutation in the coding region of the KITLG gene in any of 40 patients (upper 95% confidence limit is 7.2%).

CONCLUSION(S)

Mutations in the coding regions of the KITLG gene appear not to be a common cause of 46,XX spontaneous premature ovarian failure in North American women.

Variants in Deleted in AZoospermia-Like (DAZL) are correlated with reproductive parameters in men and women

Qualitative and quantitative defects in human germ cell production that result in infertility are common and determined at least in part by genetic factors [Matzuk and Lamb, Nat Cell Biol 4(Suppl):s41-s49, 2002]. Yet, very few genes that are associated with germ cell defects in humans have been identified. In this study, we examined whether variants of the Deleted in AZoospermia-Like (DAZL) gene are associated with measures of germ cell production in three distinct populations of men and women. We identified 95 sequence variants in DAZL and further analyzed twelve single nucleotide polymorphisms (SNPs) that were present across ethnicities. We found that seven of the twelve SNPs were associated with at least one of the parameters studied (age at premature ovarian failure or menopause, total sperm count, or total motile sperm count). Surprisingly, many alleles exhibited opposing effects in men and women, which may be a result of different genetic requirements in male and female germ cells. Single SNP and haplotype analysis suggested that SNPs in the DAZL gene may act jointly to affect common reproductive characteristics in the human population.

Premature ovarian failure

Premature ovarian failure (POF) causing hypergonadotrophic hypogonadism occurs in 1% of women. In majority of cases the underlying cause is not identified. The known causes include: (a) Genetic aberrations, which could involve the X chromosome or autosomes. A large number of genes have been screened as candidates for causing POF; however, few clear causal mutations have been identified. (b) Autoimmune ovarian damage, as suggested by the observed association of POF with other autoimmune disorders. Anti-ovarian antibodies are reported in POF by several studies, but their specificity and pathogenic role are questionable. (c) Iatrogenic following surgical, radiotherapeutic or chemotherapeutic interventions as in malignancies. (d) Environmental factors like viral infections and toxins for whom no clear mechanism is known. The diagnosis is based on finding of amenorrhoea before age 40 associated with FSH levels in the menopausal range. Screening for associated autoimmune disorders and karyotyping, particularly in early onset disease, constitute part of the diagnostic work-up. There is no role of ovarian biopsy or ultrasound in making the diagnosis. Management essentially involves hormone replacement and infertility treatment, the only proven means for the latter being assisted conception with donated oocytes. Embryo cryopreservation, ovarian tissue cryopreservation and oocyte cryopreservation hold promise in cases where ovarian failure is foreseeable as in women undergoing cancer treatments.

Mechanisms of follicular dysfunction in 46,XX spontaneous premature ovarian failure

Approximately one half of young women who have 46,XX spontaneous premature ovarian failure have ovarian follicles remaining in the ovary. These follicles function intermittently and unpredictably, and pregnancies can occur in these women without intervention, even many years after the diagnosis. Clearly, the term "premature menopause" is an inaccurate term for this condition. At present, there are no proven therapies that will improve follicular function for these women. Inappropriate luteinization related to low follicle number seems to be a major mechanism of follicular dysfunction. Autoimmune oophoritis, although apparently an uncommon cause of follicular dysfunction in these women, nonetheless presents the opportunity to develop an effective therapy to restore fertility. Young women with 46,XX spontaneous premature ovarian failure benefit from the care of a sensitive clinician, one who is willing to spend a little more time informing them about the diagnosis and referring them to other sources of information. With appropriate medical management and emotional support provided by a sensitive clinician, most young women with 46,XX spontaneous premature ovarian failure will lead happy, healthy, and fulfilling lives.