The oocyte-specific methylated region of the U2afbp-rs/U2af1-rs1 gene is dispensable for its imprinted methylation

Imprinted genes harbor discrete regions which are differentially methylated in gametes; usually the final differential methylation patterns in adults are established during embryogenesis through modifications of the initial methylation patterns in gametes. Previous reports have shown that a 200-bp region termed region II within the CpG island of the mouse imprinted U2afbp-rs gene is methylated in oocytes but not in sperm, suggesting that this region is a center for the propagation of methylated CpGs on the maternal allele and is also a candidate for an imprinting control element. To determine whether region II is required for the imprinted methylation of this gene at the endogenous locus, we generated mice carrying a deletion of this region. We herein show that parental methylation differences still exist in the CpG island on the region II-deleted allele. These findings suggest that region II is dispensable for the imprinted methylation of the U2afbp-rs gene.

Combination of automatic HPLC-RIA method for determination of estrone and estradiol in serum

We developed a highly sensitive assay for estrone and 17 beta-estradiol in serum. Estrone and 17 beta-estradiol, obtained by solid-phase extraction using a Sep pak tC18 cartridge, were purified by high-performance liquid chromatography (HPLC). Quantitation of estrone and 17 beta-estradiol were carried out by radioimmunoassay. Not insignificantly, this automatic system of extraction and HPLC succeeded in analyzing 80 samples a week. Intra-assay coefficients of variation (CV) for estrone and 17 beta-estradiol ranged from 19.5 to 28.7%, and from 8.5 to 13.7%, respectively. The minimum detectable dose for estrone and 17 beta-estradiol were 1.04 pg/ml and 0.64 pg/ml, respectively. The serum levels of 17 beta-estradiol using our method strongly correlated with those by Gas chromatography mass spectrometry (GC-MS). The serum levels of estrone and 17 beta-estradiol in 154 peri- and postmenopausal women were estimated to be between 15 and 27 pg/ml and between 3.5 and 24.0 pg/ml, respectively, while the serum level of 17 beta-estradiol in postmenopausal women, in particular, was estimated to be from 3.5 to 6.3 pg/ml. For postmenopausal women who suffered from vasomotor symptoms, the mean levels of estrone and 17 beta-estradiol at 12 to 18 hours after treatment with daily 0.625 mg conjugated equine estrogen (CEE) and 2.5 mg medroxyprogesterone acetate (MPA) were 135.0 and 21.3 pg/ml at 12 months, respectively. On the other hand, levels of estrone and 17 beta-estradiol at 12 to 18 hours after treatment with CEE and MPA every other day, were 73.4 and 15.3 pg/ml, respectively. These highly sensitive assays for estrone and 17 beta-estradiol are useful in measuring low levels of estrogen in postmenopausal women, and monitoring estrogen levels in women receiving CEE as hormone replacement therapy.

An oocyte-specific methylation imprint center in the mouse U2afbp-rs/U2af1-rs1 gene marks the establishment of allele-specific methylation during preimplantation development

An oocyte-specific methylation imprint mark region, consisting of approximately 200 bp from the mouse imprinted gene U2afbp-rs, was identified within an area containing a CpG island and a short tandem repeat sequence. The oocyte-specific methylation was preserved in fertilized eggs and then expanded on the repressed maternal allele during preimplantation development until the adult methylation pattern was achieved by 12.5 days of embryonic development. These results indicate that the oocyte-specific imprinting mark region acts as a center in establishing the hypermethylated region on the repressed maternal allele. Furthermore, a region that is hypermethylated in both gametes was identified but its hypermethylation was conserved only on the maternal allele during preimplantation development, suggesting that some factor(s) inherited from oocytes may act to maintain hypermethylation on the maternal allele.

[Determination of intratumoral estrone (E1) and estradiol (E2) in primary breast cancer tissues by sensitive HPLC-RIA]

The alternation of intratumoral estrogen metabolism has been indicated in breast cancer tissues. We determined the intratumoral concentrations of estrone (E1) and estradiol (E2) by a sensitive HPLC-radioimmunoassay (RIA) and analyzed its clinical significance in 74 primary breast cancer tissues. The average intratumoral concentrations of E1 were 48.6 + 7.3 pg/g w.w and 80.6 + 43.2 pg/g w.w in pre- and post-menopausal patients, respectively. The E2 concentrations were 168.7 + 36.8 pg/g w.w and 104.7 + 23.6 pg/g in pre- and post-menopausal patients, respectively. The background analysis demonstrated that intratumoral E2 levels were significantly higher in estrogen receptor (ER) positive tumors compared to ER negative tumors (p < 0.01). A significant correlation was also found between intratumoral E2 concentrations and progesterone receptor (PgR) status, indicating that E2 synthesis is frequently upregulated in hormone dependent tumors. These findings are important for studying the hormonal microcircumstances of Japanese breast cancer patients and also for considering the indication for clinical treatment using aromatase inhibitors.

Inactive allele-specific methylation and chromatin structure of the imprinted gene U2af1-rs1 on mouse chromosome 11

The imprinted U2af1-rs1 gene that maps to mouse chromosome 11 is predominately expressed from the paternal allele. We examined the methylation of genomic sequences in and around the U2af1-rs1 locus to establish the extent of sequence modifications that accompanied the silencing of the maternal allele. The analysis of HapII or HhaI sites showed that the silent maternal allele was hypermethylated in a block of CpG sequences that covered more than 10 kb. By comparison, the expressed paternal allele was unmethylated from a CpG island upstream of the transcribed region through 2 kb. An analysis of DNaseI hypersensitivity of a putative promoter of U2af1-rs1 showed an open chromatin conformation only on the unmethylated, expressed paternal allele. These results suggest that allele-specific hypermethylation covering the gene and its upstream CpG island plays a role in maternal allele repression of U2af1-rs1, which is reflected in altered chromatin conformation of DNaseI hypersensitive sites.

[Assessment of serum estrogen levels by RIA with HPLC during hormone replacement therapy]

We studied the serum estradiol and estrone levels in 146 peri and postmenopausal women, and in 38 women who had complained of various climacteric disturbance symptoms during daily hormone replacement therapy (HRT) with conjugated equine estrogen (CEE) 0.625 mg and medroxyprogesterone acetate (MPA) 2.5 mg. Serum estradiol and estrone were measured before treatment, and at 6 months, and after one year of the HRT therapy by HPLC-radioimmunoassay. In 146 peri and postmenopausal women, the serum level of estradiol was from 3 to 6pg/ml. The serum level of estradiol in 38 women after HRT significantly increased (p < 0.01) from 3.34 to 23.6 pg/ml at 6 months, and 21.5 pg/ml at 12 months. The serum level of estrone significantly increased (p < 0.01) from 26.6pg/ml to 156.7pg/ml at 6 months, and 137.2pg/ml at 12 month. These results are very useful for deciding on the doses of hormones and the expected serum estradiol level in HRT for Japanese women.

Amino acid sequence of two sea anemone toxins from Anthopleura fuscoviridis

The amino acid sequences of two toxins, AFT-I and AFT-II, from the sea anemone Anthopleura fuscoviridis were determined. AFT-I and -II consist of 47 and 48 amino acid residues, respectively, and are cross-linked with three disulfide bridges. The sequences have high homology to those of toxins I and II from Anemonia sulcata and anthopleurin-A and -B from Anthopleura xanthogrammica.