POF Syndrome
A premature failure of oocyte maturation also called “POF syndrome” is very common, affecting 1% of the female population. Around 30% of cases are considered to be caused by a gene defect. The most well-known genetic cause of the POF syndrome is Turner’s syndrome (45,XO karyotype), as it can be detected easily in the patient´s chromosome picture.
The definition of the POF is based on patient age. The average age of the natural menopause in Germany is 51 years, although there is a wide margin of variation. If the menopause occurs before the age of 40, the woman is said to suffer from early menopause, i.e. POF syndrome. Alongside genetic causes, also nuclear or mitochondrial autoimmune diseases, galactosaemia, tumors, viral infections or myasthenia gravis may trigger POF. After radio- or chemotherapy, drug consumption or stress, a POF syndrome is often initiated as a secondary consequence.
The now existing merely non-genetic clinical diagnostic approaches for identifying POF can be significantly improved by a molecular functional expression analysis of genes probably causing the POF syndrome (POF candidate genes). Such studies will also help to subdivide the large and heterogeneous group of patients into more homogeneous clinical subgroups.
What are POF candidate genes ?
POF candidate genes are particularly the master genes of female germ cell maturation (folliculogenesis). We can expect that a POF syndrome may be caused by mutations in each of these genes. But how frequent is a particular gene mutation identified? In general terms, we can predict that the frequency of functionally disrupting gene mutations in a random female population is low, ranging between 1:100.000 and 1:1.000.000. For this reason, it is important to select clinical sub-groups of patients with the aid of ultrasound analysis and laparoscopy already before a comprehensive molecular genetic analysis programme. It would help to pinpoint the possible phase(s) in which the germ cell maturation of the patient is interrupted. By taking the patient’s clinical history and its family history, the doctor will also try to exclude any non-genetic cause of the POF syndrome as far as possible.
As part of this clinical routine diagnosis, a chromosomal analysis to detect especially any large X-chromosomal aberrations in this patient group is strongly recommended.
Patients with a normal karyotype (46,XX) are then inivited to participate voluntary and without any costs in our current molecular POF candidate gene diagnostic screening programme. For this purpose the patient’s DNA and RNA is extracted from her leukocytes. If gonadal tissue has been gained by a laparoscopic ovarian biopsy carried out for histological diagnosis purposes it should be examined for analysis of the phase in which the patient´s folliculogenesis has been interrupted by expression assays of some master folliculogenesis genes.
Criteria for the inclusion or exclusion of patients in our POF study
All patients presenting in our department in the Hormone Clinic or Infertility Clinic legen, and recognised with a disorder with clinical and endocrinological symptoms of an idiopathic POF syndrome are recommended to join the POF candidate gene expression study after having agreed also to a chromosomal analysis. The inclusion criteria are a primary or secondary hypergonadotropic, hypooestrogenic amenorrhoea with FSH levels above 20 mU/ml. The patients must also be aged younger than 40. Other possible causes of the POF syndrome must be excluded prior to genetic diagnosis by answering a detailed questionaire.
Molecular diagnosis in the lab usually starts by extracting first a DNA and RNA sample from a patient´s blood sample which are usually better accessible than samples of follicular tissue and germ cells. DNA/RNA diagnosis requires
20 ml of whole blood sent to the lab in an EDTA tube.
Together with the blood sample the patient history questionnaire to POF questionaire must be sent as well including all clinical data and any copies of previous diagnostic findings. Residual ovarian material from a biopsy (if available) is collected in a special cryo-tube and snap-frozen immediately after surgical removing on dry ice or plunged in liquid nitrogen. The frozen tissue samples are sent directly to Heidelberg in a dry ice box. Ovarian tissue samples fixes with buffered formaline are used to cut paraffin sections for targeted immunohistochemical diagnosis of the expression profile of selected folliculogenesis genes by immunohistochemistry and in situ RNA analysis.
On personal request, the patient will get a written protocol containing the results of her genetic POF diagnosis herself or via the counselling docter as soon as possible and the data are added to her medical record. However, please keep in mind that the results are available not sooner than 2 months after the blood and tissue samples are taken.
No further risks are incurred by a patient undergoing the examination. Both the blood samples and the ovarian biopsy are part of a necessary clinical diagnostic laparoscopy and therefore part of the routine clinical examination.
Before the genetic diagnosis starts, patients are informed personally and with written consent about the content and scope of the molecular genetic examination, especially the potential health benefits and risks. The patients’ names and any other confidential information are subject to medical confidentiality and the provisions of the Federal Privacy Act. Third parties are allowed no access to the original patient documents.
