Abstract
PurposeVariations in many genes may lead to the occurrence of oocyte maturation defects. To investigate the genetic basis of oocyte maturation defects, we performed clinical and genetic analysis of a pedigree.MethodsThe proband with oocyte maturation defect-2 receiving ovulation induction therapy and her parents were selected for clinical detection, whole exome sequencing and Sanger sequencing. One unrelated healthy woman received ovulation induction therapy as control. Mutations were assessed after frequency screening of public exome databases. Then homozygous variants shared by the proband and her parents were selected.ResultsArrest of oocytes maturation was observed. A new missense mutation in TUBB8 (TUBB8: NM_177,987: exon 2: c. C161T: p. A54V) was identified, which was shown to be rare compared with public databases. The variant was highly conserved among primates, and was suggested to be deleterious by online software prediction.ConclusionsThe homozygote of this variant (TUBB8: NM_ 177,987: exon 2:c.C161T: p.A54V) might affect spindle assembly, cause arrest of oocyte maturation and lead to oocyte maturation defect-2.
Highlights
In the fetal ovary, oocytes pause at prophase I
During each of the 3 cycles of treatment, oocytes were retrieved from the patient and all oocytes were observed at the Germinal vesicle (GV) stage and metaphase I (MI) stage under a microscope (Fig. 3)
After a cycle of ovulation induction treatment, most oocytes of the healthy individual were at the metaphase II (MII) stage (Fig. 4)
Summary
The maturation process of oocytes begins, and oocytes resume meiosis with a surge of luteinizing hormone. Germinal vesicle (GV) breakdown, spindle assembly, chromosomal migration, asymmetric division, and extrusion of the first polar body occur in turn. The oocytes arrest at metaphase II (MII) until fertilization [1, 2]. Primary infertility or failure of in vitro fertilization (IVF) were the clinical manifestation of oocyte maturation defects (OOMDs). Failure of GV breakdown, absence of the first polar body, and failure to progress beyond MII could result in arrest of oocyte maturation [3]
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