The Eye

Broekhuyse, R.M.; Daemen, F.J.M.

doi:10.1007/978-1-4684-0865-2_5

Cited by 10 publications

(7 citation statements)

References 120 publications

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“…The aand 3-crystallins represent early-stage markers, with a-crystallin expressed earliest and distributed throughout the epithelial and fiber cell compartments (Zwann, 1983) and 3-crystallin expressed initially in equatorial cells and in lens fiber cells subsequently (McAvoy, 1980;Piatigorsky, 1981). Expression of the y-crystallins (McAvoy, 1980;Piatigorsky, 1981) and MIP26 (Broekhuyse et al, 1976;Vermorken et al, 1977) is restricted to the central lens fiber cells. ; only a-crystallin is shown), indicating that expression of early-stage differentiation markers was unaffected.…”

Section: Resultsmentioning

confidence: 99%

Contrasting roles for c-Myc and L-Myc in the regulation of cellular growth and differentiation in vivo.

et al. 1995

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Although myc family genes are differentially expressed during development, their expression frequently overlaps, suggesting that they may serve both distinct and common biological functions. In addition, alterations in their expression occur at major developmental transitions in many cell lineages. For example, during mouse lens maturation, the growth arrest and differentiation of epithelial cells into lens fiber cells is associated with a decrease in L‐ and c‐myc expression and a reciprocal rise in N‐myc levels. To determine whether the down‐regulation of L‐ and c‐myc are required for mitotic arrest and/or completion of differentiation and whether these genes have distinct or similar activities in the same cell type, we have studied the consequences of forced L‐ and c‐myc expression in the lens fiber cell compartment using the alpha A‐crystallin promoter in transgenic mice (alpha A/L‐myc and alpha A/c‐myc mice). With respect to morphological and molecular differentiation, alpha A/L‐myc lenses were characterized by a severely disorganized lens fiber cell compartment and a significant decrease in the expression of a late‐stage differentiation marker (MIP26); in contrast, differentiation appeared to be unaffected in alpha A/c‐myc mice. Furthermore, an analysis of proliferation indicated that while alpha A/L‐myc fiber cells withdrew properly from the cell cycle, inappropriate cell cycle progression occurred in the lens fiber cell compartment of alpha A/c‐myc mice. These observations indicate that continued late‐stage expression of L‐myc affected differentiation processes directly, rather than indirectly through deregulated growth control, whereas constitutive c‐myc expression inhibited proliferative arrest, but did not appear to disturb differentiation. As a direct corollary, our data indicate that L‐Myc and c‐Myc are involved in distinct physiological processes in the same cell type.

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Section: Resultsmentioning

confidence: 99%

Contrasting roles for c-Myc and L-Myc in the regulation of cellular growth and differentiation in vivo.

et al. 1995

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“…These data suggest that the sphingomyelin-rich lens fiber cell membrane provides the ideal lipid milieu for forming very stable cholesterol domains. It is also interesting to note that nuclear lens membranes contain greater amounts of sphingomyelin (36) and saturated fatty acids (9) than do cortical membranes. This observation would suggest that cholesterol domains occur more readily in the lens nucleus, possibly explaining the fact that the diffraction peaks corresponding to the cholesterol domains in the intact nuclear samples were more well defined than in the intact cortical samples (compare Fig.…”

Section: Figmentioning

confidence: 99%

Direct Evidence for Immiscible Cholesterol Domains in Human Ocular Lens Fiber Cell Plasma Membranes

Jacob¹,

Cenedella

Mason³

1999

Journal of Biological Chemistry

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The molecular structure of human ocular lens fiber cell plasma membranes was examined directly using small angle x-ray diffraction approaches. A distinct biochemical feature of these membranes is their high relative levels of free cholesterol; the mole ratio of cholesterol to phospholipid (C/P) measured in these membranes ranges from 1 to 4. The organization of cholesterol in this membrane system is not well understood, however. In this study, the structure of plasma membrane samples isolated from nuclear (3.3 C/P) and cortical (2.4 C/P) regions of human lenses was evaluated with x-ray diffraction approaches. Meridional diffraction patterns obtained from the oriented membrane samples demonstrated the presence of an immiscible cholesterol domain with a unit cell periodicity of 34.0 Å, consistent with a cholesterol monohydrate bilayer. The dimensions of the sterol-rich domains remained constant over a broad range of temperatures (5-20°C) and relative humidity levels (31-97%). In contrast, dimensions of the surrounding sterol-poor phase were significantly affected by experimental conditions. Similar structural features were observed in membranes reconstituted from fiber cell plasma membrane lipid extracts. The results of this study indicate that the lens fiber cell plasma membrane is a complex structure consisting of separate sterol-rich and -poor domains. Maintenance of these separate domains may be required for the normal function of lens fiber cell plasma membrane and may interfere with the cataractogenic aggregation of soluble lens proteins at the membrane surface.

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“…The higher level of cholesterol in bovine lens nuclear lipid (59 mol %) than cortical lipid (36 mol %) may be required to compensate for differences in the phospholipid and fatty acid composition of the two regions. Nuclear lipids are enriched in sphingomyelin (Broekhuyse and Daemen, 1977) and saturated fatty acids (Li and Spector, 1987) compared with cortical lipid.…”

Section: Introductionmentioning

confidence: 99%