Analysis of partner of inscuteable (mPins) expression in the developing mouse eye

PURPOSE

Asymmetric cell division (ACD) is the fundamental mechanism underlying the generation of cellular diversity in invertebrates and vertebrates. During Drosophila neuroblast division, this process involves stabilization of the apical complex and interaction between the Inscuteable (Insc) and Partner of inscuteable (Pins) proteins. Both cell-intrinsic factors and cell-cell interactions seem to contribute to cell fate decisions in the retina. The Pins protein is known to play a major role in the asymmetric segregation of cell fate determinants during development of the central nervous system in general, but its role in asymmetric cell divisions and retinoblast cell fate has never been explored. The primary aim of this study was to determine the spatial distribution and time course of mouse homolog of Drosophila Partner of Inscuteable (mPins) expression in the developing and adult mouse eye.

METHODS

The expression pattern of mPins was studied in the mouse eye from embryonic (E) stage E11.5 until adulthood, by semiquantitative RT-PCR, in situ hybridization, and immunohistochemistry. In addition, variations in mRNA and protein levels for mPins were analyzed in the developing postnatal and adult lens, by semiquantitative RT-PCR, western blot analysis, in situ hybridization, and immunohistochemistry.

RESULTS

We detected mPins mRNA at early stages of mouse embryonic eye development, particularly in the neuroblastic layer. In early postnatal development, mPins mRNA was still detected in the neuroblastic layer, but also began to be detectable in the ganglion cell layer. Thereafter, mPins mRNA was found throughout the retina. This pattern was maintained in differentiated adult retina. Immunohistochemical studies showed that mPins protein was present in the neuroblastic layer and the ganglion cell layer during the early stages of postnatal retinal development. At these stages, mPins protein was colocalized with Numb protein, a marker of the ACD. At later postnatal stages, mPins protein was present in all retinal nuclear layers and in the inner plexiform layer. It continued to be detected in these layers in the differentiated retina; the outer plexiform layer and the photoreceptor inner segments also began to display positive immunostaining for mPins. In the adult retina, mPins was also detected in the retinal pigment epithelium and choroidal melanocytes. Throughout development, mPins protein was detected in nonretinal tissues, including the cornea, ciliary body, and lens. We focused our attention on lens development and showed that mPins protein was first detected at E14.5. The most striking results obtained concerned the lens, in which mPins protein distribution switched from the anterior to the posterior region of the lens during embryonic development. Interestingly, in the postnatal and adult lens, mPins protein was detected in all lens cells and fibers.

CONCLUSIONS

We provide the first demonstration that mPins protein is expressed from embryonic stages until adulthood in the mouse eye. These results suggest that mPins plays important roles in eye development. This work provides preliminary evidence strongly supporting a role for mPins in the asymmetric division of retinoblasts, and in the structure and functions of adult mouse retina. However, the link between the presence of mPins in different ocular compartments and the possible occurrence of asymmetric cell divisions in these compartments remains to be clarified. Further studies are required to elucidate the in vitro and in vivo functions of mPins in the developing and adult human eye.

The RNA-binding protein Musashi-1 is produced in the developing and adult mouse eye

PURPOSE

Musashi-1 (Msi1) is an RNA-binding protein produced in various types of stem cells including neural stem/progenitor cells and astroglial progenitor cells in the vertebrate central nervous system. Other RNA-binding proteins such as Pumilio-1, Pumilio-2, Staufen-1, and Staufen-2 have been characterized as potential markers of several types of stem or progenitor cells. We investigated the involvement of Msi1 in mouse eye development and adult mouse eye functions by analyzing the profile of Msi1 production in all ocular structures during development and adulthood.

METHODS

We studied Msi1 production by in situ hybridization and immunohistochemistry of ocular tissue sections and by semi-quantitative RT-PCR and western blot analysis from the embryonic stage of 12.5 days post coitum (E12.5 dpc) when the first retinal ganglion cells (RGCs) begin to appear to the adult stage when all retinal cell types are present.

RESULTS

Msi1 mRNA was present at all studied stages of eye development. Msi1 protein was detected in the primitive neuroblastic layer (NbL), the ganglion cell layer (GCL), and in all major differentiated neurons of postnatal developing and adult retinae. During postnatal developing stages, faint diffuse Msi1 protein staining is converted to a more specific distribution once mouse retina is fully differentiated. The most striking result of our study concerns the large amounts of Msi1 protein and mRNA in several unexpected sites of adult mouse eyes including the corneal epithelium and endothelium, stromal keratocytes, progenitor cells of the limbus, equatorial lens stem cells, differentiated lens epithelial cells, and differentiating lens fibers. Msi1 was also found in the pigmented and nonpigmented cells of the ciliary processes, the melanocytes of the ciliary body, the retinal pigment epithelium, differentiated retinal neurons, and most probably in the retinal glial cells such as Müller glial cells, astrocytes, and the oligodendocytes surrounding the axons of the optic nerve. Msi1 expression was detected in the outer plexiform layer, the inner plexiform layer, and the nerve fiber layer of fully differentiated adult retina.

CONCLUSIONS

We provide here the first demonstration that the RNA-binding protein, Msi1, is produced in mouse eyes from embryonic stages until adulthood. The relationship between the presence of Msi1 in developing ocular compartments and the possible stem/progenitor cell characteristics of these compartments remains unclear. Finally, the expression of Msi1 in several different cell types in the adult eye is extremely intriguing and should lead to further attempts to unravel the role of Msi1 in cellular and subcellular RNA metabolism and in the control of translational processes in adult eye cells particularly in adult neuronal dendrites, axons, and synapses.

Gamma-D crystallin gene (CRYGD) mutation causes autosomal dominant congenital cerulean cataracts

Congenital cataracts are a major cause of bilateral visual impairment in childhood. We mapped the gene responsible for autosomal congenital cerulean cataracts to chromosome 2q33-35 in a four generation family of Moroccan descent. The maximum lod score (7.19 at recombination fraction theta=0) was obtained for marker D2S2208 near the gamma-crystallin gene (CRYG) cluster. Sequencing of the coding regions of the CRYGA, B, C, and D genes showed the presence of a heterozygous C>A transversion in exon 2 of CRYGD that is associated with cataracts in this family. This mutation resulted in a proline to threonine substitution at amino acid 23 of the protein in the first of the four Greek key motifs that characterise this protein. We show that although the x ray crystallography modelling does not indicate any change of the backbone conformation, the mutation affects a region of the Greek key motif that is important for determining the topology of this protein fold. Our data suggest strongly that the proline to threonine substitution may alter the protein folding or decrease the thermodynamic stability or solubility of the protein. Furthermore, this is the first report of a mutation in this gene resulting in autosomal dominant congenital cerulean cataracts.

Regulation of prolactin secretion during pregnancy and lactation

Prolactin plays major roles in maintaining the corpora lutea of pregnancy and in the synthesis of milk during lactation. The hypothalamic mechanisms involved in these functions have been investigated. Mating leads to a surge of prolactin and programs daily surges during early pregnancy. The expression of Fos-immunoreactivity shows that mating activates several hypothalamic nuclei, particularly the arcuate nucleus and medial preoptic area. In the arcuate nucleus, mating is associated with Fos expression in beta-endorphin neurons, and infusion of naloxone blocks both mating-induced and diurnal prolactin surges. Tyrosine hydroxylase-immunoreactive dopamine neurons appear not to participate in surge generation. However, after day 10 of gestation the secretion of placental lactogens suppresses prolactin secretion via activation of dopamine neurons without involvement of beta-endorphin neurons. Intracerebroventricular implantation of placental lactogen-secreting cells will block pregnancy prolactin surges, increase Fos expression in dopamine neurons, and increase tyrosine hydroxylase activity. During lactation the mechanisms regulating dopamine and beta-endorphin neurons are further modified. In early lactation a prolactin-induced increase in tyrosine hydroxylase activity leads to negative feedback, but this effect is lost by mid-lactation. Overriding this negative feedback is the inhibitory effect that suckling has on dopaminergic activity. This may involve beta-endorphin-mediated inhibition of dopamine neurons, as naloxone causes a marked increase in tyrosine hydroxylase activity and suppression of circulating prolactin. However, removal of tonic dopamine inhibition is not sufficient to account for the high levels of prolactin attained during lactation, and additional releasing factors are probably involved. In situ hybrization histochemistry for the most recent candidate, prolactin-releasing peptide, suggests that this may involve brain stem neurons that co-localize noradrenaline. Thus, prolactin secretion during pregnancy and lactation involve complex interactions of regulatory factors and plasticity of neuronal responsiveness.

Elevated level of follicular fluid vascular endothelial growth factor is a marker of diminished pregnancy potential

OBJECTIVE

To evaluate whether differences in follicular fluid vascular endothelial growth factor (FF VEGF) concentrations are observed between women achieving a clinical pregnancy and those failing to conceive.

DESIGN

Retrospective chart review and analysis of FF VEGF concentrations.

SETTING

University teaching center.

PATIENT(S)

Fifty-seven women < or =42 years of age undergoing follicular aspiration in preparation for IVF or GIFT.

INTERVENTION(S)

Analysis of FF VEGF concentrations and chart review of a single IVF or GIFT cycle.

MAIN OUTCOME MEASURE(S)

Follicular fluid VEGF concentrations, clinical pregnancy rate, age, ampules of gonadotropins used, oocytes retrieved, peak estradiol serum concentrations, day 3 FSH levels, and fertilization rate.

RESULT(S)

Women who did not conceive had higher FF VEGF concentrations than women achieving a clinical pregnancy (4.409 + 2,387 versus 2.793 +/- 1,180 pg/mL: P < .001). A negative correlation was observed between FF VEGF concentrations and peak estradiol levels and number of oocytes retrieved. A positive correlation was found for FF VEGF and patient's age and ampules of gonadotropins used.

CONCLUSION(S)

Elevated FF VEGF concentrations are associated with poor conception rates after IVF or GIFT.

Effects of chronic hyperprolactinemia on tuberoinfundibular dopaminergic neurons

Prolactin (PRL) secretion is under the inhibitory regulation of the tuberoinfundibular dopaminergic (TIDA) system. Short-term elevation in PRL levels has been shown to increase the activity of TIDA neurons, however, the responsiveness of TIDA neurons to chronically elevated serum PRL levels is controversial. The purpose of this study was to investigate the effects of prolonged elevations of serum PRL on TIDA neuronal activity. Female Sprague-Dawley rats (2-3 months old) were ovariectomized and implanted (s.c.) with haloperidol (HAL), a dopamine receptor antagonist for 6 or 9 months to produce hyperprolactinemia. Ovariectomized, sham-implanted rats were used as controls. Other groups of intact rats were implanted with HAL or sham-implanted for 9 months and then were implanted with PRL-producing MMQ cells for 6 weeks to further increase circulating PRL levels. TIDA neuronal activity was measured in terms of tyrosine hydroxylase (TH) activity in the stalk-median eminence and was correlated with changes in serum PRL levels. After 6 months of treatment, TH activity in HAL-treated rats was 130% higher than that in the control rats. After 9 months of treatment, TH activity in HAL-treated rats was 81% higher than that in control rats. This increase was significantly less than the increase that occurred after 6 months of treatment. Nine months of HAL-induced hyperprolactinemia followed by implantation of PRL-producing MMQ cells, which resulted in very high levels of PRL, did not increase TH activity in the stalk-median eminence. These results demonstrate that hyperprolactinemia over a prolonged period reduces the responsiveness of TIDA neurons, and these effects vary depending on the duration and intensity of hyperprolactinemia.

Follicular fluid vascular endothelial growth factor concentrations are elevated in women of advanced reproductive age undergoing ovulation induction

OBJECTIVE(S)

To determine whether follicular fluid (FF) from women of advanced reproductive age had a relative deficiency of the angiogenic cytokine vascular endothelial growth factor/vascular permeability factor. Furthermore, we sought to determine whether luteinized granulosa cells secrete vascular endothelial growth factor/vascular permeability factor in response to hypoxia.

DESIGN

Retrospective cohort study.

SETTING

University teaching hospital.

PATIENTS

Women undergoing follicular aspiration after superovulation in preparation for IVF-ET. Women of advanced reproductive age consisted of 21 women > or = 38 years old (range, 38 to 46 years); 15 subjects < or = 30 years served as the control population.

INTERVENTION(S)

Granulosa cells and FF were collected by transvaginal aspiration 35 hours after hCG. Granulosa cells from two women were cultured for 24 and 48 hours in M199 + 10% fetal bovine serum in 1% O2-5% CO2-94% N2 (hypoxic) or 95% air-5% CO2 (normoxic) without or with 0.1 mol/L cobalt chloride.

MAIN OUTCOME MEASURE(S)

Pooled FF vascular endothelial growth factor/vascular permeability factor concentrations and media vascular endothelial growth factor/vascular permeability factor accumulation at 24 and 48 hours were determined.

RESULT(S)

Follicular fluid vascular endothelial growth factor/vascular permeability factor concentrations were higher in advanced reproductive age women compared with younger women (3,735 +/- 2,155 versus 2,205 +/- 952 pg/mL, mean +/- SD). Accumulation of vascular endothelial growth factor/vascular permeability factor at 24 and 48 hours was 391 +/- 54 and 744 +/- 2 pg/mL in media maintained in 5% CO2 and air. Cobalt chloride induced a marked increase in vascular endothelial growth factor/vascular permeability factor (2,008 +/- 52 pg/mL at 24 hours and 3,630 +/- 519 pg/mL at 48 hours). An intermediate but significant increase in vascular endothelial growth factor/vascular permeability factor (733 +/- 35 pg/mL at 24 hours and 2,675 +/- 864 pg/mL at 48 hours) was observed with 1% O2 compared with normoxic controls.

CONCLUSION(S)

After hMG and hCG administration the FF from women of advanced reproductive age showed increased vascular endothelial growth factor/vascular permeability factor concentrations compared with younger women. Increased vascular endothelial growth factor/vascular permeability factor concentrations could be consistent with a hypoxic environment within follicles of older women.

Effect of preclotting and precoating agents on seeded venous grafts

This study evaluated the effect of whole blood preclotting (WB), fibronectin (FB) and "Cell Tak" (CT) precoating on the patency rate of seeded vena cava grafts. Ten cm x 8 mm ID ringed PTFE grafts were implanted in the vena-cavae of 29 dogs. Aspirin (325 mg po qd) was administered pre-operatively and continued post-operatively. After preclotting or precoating, all grafts were seeded with porcine endothelial cells. The 32 day patency rates were: 67%, 67% and 37% for WB, FB and CT, respectively (p less than 0.5 CT vs FB, WB). Endothelialized surfaces ranged from 67 +/- 35, 43 +/- 41 to 28 +/- 45% respectively for WB, FB and CT (p less than 0.05 CT vs WB). Preclotting time was shortest for WB technique. We conclude that: 1) FB and WB grafts have the highest patency rate with WB preclotting being a more cost effective and less time consuming technique; 2) endothelial seeding and Aspirin may make vena cava grafting possible.

Cholesteryl ester metabolism in tissue culture cells: II. Source of accumulated esterified cholesterol in Fu5AH rat hepatoma cells

Previous investigations had demonstrated that Fu5AH rat hepatoma cells accumulated large quantities of esterified cholesterol when grown in hyperlipemic rabbit serum. The present investigation has determined the sources of the cellular esterified cholesterol when the cells were grown in hyperlipemic serum. Cellular esterification of endogenous and exogenous free cholesterol contributed 10% and 30%, respectively. The remaining 60% of the accumulated cellular esterfied cholesterol was derived from exogenous (serum) cholesteryl esters. Evidence for the hydrolysis of a portion of the incorporated esterified cholesterol is presented. A stimulation of free cholesterol incorporation and cellular esterification is elicited by hyperlipemic serum and serum lipoproteins when compared to normolipemic serum present at equivalent exogenous cholesterol concentrations. The effect of hyperlipemic serum is reduced by Tween-80 and Triton WR-1339. Comparative data on esterified cholesterol accumulation, free cholesterol incorporation, and cellular cholesterol esterification in Fu5-5 rat hepatoma cells, L-cells, and rabbit aortic medial cells are presented.