Cell surface carbohydrate changes during embryonic and fetal skin development

Comparison of lectin binding patterns in malformed and normal human embryos and fetuses

Altered glycosylation in the course of disease detectable by changes in lectin binding patterns has been well established for adult tissues, but only a few authors have described carbohydrate entities during normal human embryonic and fetal development. Whether alterations in carbohydrate patterns occur in human embryonic and fetal tissues, affected by malformations, remains to be investigated. We, therefore, examined human embryos and fetuses at corresponding developmental stages with and without malformations (spina bifida, exencephaly, cleft lip and cleft palate, and dysmelia) with respect to their lectin binding patterns for the lectins RCA I, PNA, WGA, SBA, SNA, Con A, and LTA. Our results demonstrated that during the development of malformations, the affected tissue sites exhibited a different carbohydrate pattern from normally developed specimens. Furthermore, tissues known to be sites of secondary malformation, accompanying the primary defect, although displaying a histologically normal appearance, also showed an altered carbohydrate pattern. This might indicate a possible general alteration in the carbohydrate pattern in the course of development of malformations in man.

Expression of Lewis Y (Le(y)) antigen in human anagen hair follicles

Lewis Y (Le(y)) antigen, a difucosylated tetrasaccharide found on type 2 blood group oligosaccharides of glycolipids and glycoproteins, is thought to be a phenotypic marker predictive of cell differentiation. The distribution of this antigen in human anagen hair follicles was examined by immunohistochemical staining using a monoclonal antibody (AH-6) to Le(y). In the bulbar and suprabulbar portion of anagen hair follicles, Le(y) antigen was detected in the three layers of the inner root sheath. Subsequently, the positive staining became translocated to the innermost layer of the outer root sheath in the middle part of the hair follicles. In the upper portion of the hair follicles, Le(y) antigen was found in the outer cells of the outer root sheath. These findings suggested that the expression of Le(y) antigen in the anagen hair follicles was correlated with the processes of keratinization or terminal differentiation.

Monoclonal antibody E6G6 recognizes glycolipids as a differentiation antigen in Shope carcinoma cells

Monoclonal antibody E6G6 preferentially reacted with well differentiated and non-tumorigenic Shope carcinoma cell lines but hardly reacted with undifferentiated and tumorigenic lines as determined by enzyme-linked immunosorbent assay, cytofluorometry and the complement dependent cytotoxicity test. Immunohistochemical analysis of the primary carcinoma tissue revealed that the antibody intensely stained keratinizing carcinoma cells with marked shrinkage whereas it did not stain normal epidermal keratinizing rabbit cells or benign tumor (Shope papilloma) cells, suggesting that the antigen expression in vivo was closely correlated with terminal differentiation of the carcinoma cells. Thin layer chromatography immunostaining revealed that the antigen was comprised of several neutral glycolipids and that differentiated cells contained about ten times more antigen than undifferentiated cells.

Human epidermal keratinocyte expression of sialyl-Lewis X

Cell-surface oligosaccharides can function as ligands for intercellular adhesion receptors, matrix proteins, and growth factors. We report that human neonatal and adult epidermal keratinocytes (KC) express sialyl Lewis X [s-Le(x); SA alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-3R], a ligand for endothelial and platelet selectins. Freshly isolated or cultured KC bind FH6 monoclonal antibody (MoAb), which is specific for s-Le(x)-containing oligosaccharides. The relevant epitope is bona fide s-Le(x), because sialidase treatment of KC suspensions abrogates FH6 binding while generating de novo KC reactivity with anti-Le(x). KC stained in ice-cold suspension display a knobby membrane distribution of s-Le(x) detectable by immunofluorescence microscopy. As others have reported, FH6 appeared not to bind KC in perpendicular skin sections. However, basal KC in intact epidermal sheets exhibited obvious "honeycomb" reactivity with FH6 when stained and viewed en face, suggesting that s-Le(x) in intact epidermis may occur in bands that parallel the major tissue axis. FH6 specifically immunoprecipitated proteins of Mr 34 kd, 44 kd, and 56 kd from [35S]-labeled KC, and anti-Le(x) precipitated similar proteins from sialidase-treated KC. The enzymatic basis for KC s-Le(x) expression was studied by analyzing acceptor specificities and other properties of KC fucosyltransferases. Results indicate that KC express both Lewis- and myeloid-type alpha 1-3fucosyltransferases. KC s-Le(x) could be an important element of the epithelial milieu, because both epithelial cells and immune cells that home to epithelia express s-Le(x) and related structures, and because KC s-Le(x) is well positioned for selectin-mediated platelet binding after trans-cutaneous wounding. The apparent distributions of s-Le(x) in epidermis and on isolated KC are compatible with a functional role for s-Le(x) in these intercellular interactions.

Human keratinocytes express a new CD44 core protein (CD44E) as a heparan-sulfate intrinsic membrane proteoglycan with additional exons

We previously identified a 90-kD (GP90), collagen-binding, membrane glycoprotein, termed extracellular matrix receptor III (ECMR III), that is homologous to the lymphocyte homing receptor and CD44 antigen (Gallatin, W. M., E. A. Wayner, P. A. Hoffman, T. St. John, E. C. Butcher, and W. G. Carter. 1989. Proc. Natl. Acad. Sci. USA. 86:4654-4658). CD44 is abundantly expressed in many epithelial tissues, and is localized predominantly to filopodia in cultured keratinocytes. Here we establish CD44 as a polymorphic family of related membrane proteoglycans and glycoproteins possessing extensive diversity in both glycosylation and core protein sequence. Human neonatal foreskin keratinocytes (HFKs) and QG56 lung squamous carcinoma cells express an alternatively spliced form of the CD44 core protein (termed CD44E) that contains an additional 132 amino acids in the carbohydrate attachment region of the extracellular domain. HFKs, HT1080 fibrosarcoma and QG56 cells, as well as many other human cells, contain varying ratios of GP90 and structurally related, higher molecular mass forms of CD44 that express the following characteristics: (a) each form reacted with anti-CD44 (mAbs) P1G12, P3H9, and P3H5. Each of these mAbs recognized a distinct, nonoverlapping epitope present on each CD44 form. (b) Differences in mass were due primarily to variation in carbohydrate moieties, including sulfated aspargine-linked glycopeptides (GP), chondroitin sulfate (CS), and heparan sulfate (HS) glycosaminoglycans, as well as O-linked mucin and polylactosamine structure(s). The major polymorphic forms were designated HT1080 GP90 and CS180, QG56 GP230, and HFK HS/CS250, based on dominant carbohydrate moieties and relative mass. (c) The polymorphic forms use CD44 and CD44E core proteins, each containing a unique set of potential attachment sites for O- and N-glycosides and glycosaminoglycans. (d) Immunofluorescence microscopy, differential extraction with Triton-X-114 detergent, and incorporation into liposomes indicated that all the forms were membrane bound glycoconjugates. These results define CD44 as a structurally diverse, but immunologically related, set of intrinsic membrane macromolecules, and suggests that these structurally varied forms might be expected to manifest multiple functions.

Human keratinocytes contain carbohydrates that are recognized by keratan sulfate-specific monoclonal antibodies

Monoclonal antibodies that recognize carbohydrate epitopes found in keratan sulfate glycosaminoglycan chains identified both intracytoplasmic and cell-surface carbohydrates of human keratinocytes. These carbohydrates were detected, using indirect immunoperoxidase methods, both in sections of paraffin-embedded tissues and in intact cultured keratinocytes. Of the seven anti-keratan sulfate monoclonal antibodies used in this study, five detected significant amounts of epitopes associated with keratinocytes. This indicates that only certain, specific types of keratan sulfate-like carbohydrates were expressed by these cells. The extent and localization of keratan sulfate-like carbohydrates appeared to be closely related to the differentiation status of cultured keratinocytes. These epitopes were very weakly expressed on surfaces of all monolayer keratinocytes, but flattened, suprabasal cells in high Ca++ cultures strongly expressed keratan sulfate-like carbohydrates on their surfaces. A much larger population of cultured keratinocytes expressed intracellular keratan sulfate-like carbohydrates identified by the same five antibodies that detected surface epitopes. In monolayer cells, keratan sulfate-like carbohydrates were predominantly found in a broad perinuclear zone. In addition, three of the five immunoreactive antibodies detected epitopes that appeared at cell boundaries, specifically at sites of close cell-to-cell contact. Thus, molecules bearing carbohydrates recognized by anti-keratan sulfate antibodies appear at developmentally important stages of keratinocyte differentiation, indicating that these carbohydrates may serve as markers for molecules important in the differentiation of human keratinocytes.

Common antigen expression between human periderm and other tissues identified by GB1-monoclonal antibody

From 4 weeks estimated gestational age (EGA) until the end of the second trimester (24 weeks EGA) the fetal epidermis is covered by a specialised epithelium, the periderm. The origin and function of periderm remain speculative. We have demonstrated, using indirect immunofluorescence and immunoperoxidase staining, that periderm is recognised by a mouse IgM monoclonal antibody (Mab) GB1, which has been raised against a simple extract of human amnion. Immunoelectron microscopy localises GB1 to the amniotic surface of periderm, particularly in association with the microvilli, and also bordering cellular identations of the periderm cells. GB1 antigen (ag) is also expressed by the epithelium of fetal oesophagus, fetal and adult conjunctiva and cornea but is absent in a variety of other fetal and adult tissues including bladder, oral mucosa and thymus. The similar distribution of GB1 ag in both periderm and membranes possibly suggests a common origin and the shared expression with fetal oesophagus and fetal and adult eye may indicate a function related to the fluid environment. We therefore feel that GB1 Mab may be of use in further investigations into the origin, structure and function of human periderm.

The structure of fucosylated blood group substances in fetal rat skin. The combined use of monoclonal antibodies and glycosyl hydrolases

Cell surface carbohydrates are thought to be important during embryonic development. We have studied a group of defined cell surface carbohydrates during the differentiation of fetal rat skin by the use of immunocytochemical techniques. We used monoclonal antibodies to the LeX and human blood group H type II haptens. The structure of the molecules carrying these haptens has been inferred by the sensitivity of the immune reactions to digestion by glycosyl hydrolases. The primitive ectoderm expressed the LeX hapten. The differentiating epidermis carries the H type II antigen, but this was only detected following cleavage of a terminally modified portion of the carbohydrate containing linear poly-N-acetyl lactosamine chains. These carbohydrates on epidermal cells are carried N linked to glycoproteins.

Ontogeny of structural components at the dermal-epidermal junction in human embryonic and fetal skin: the appearance of anchoring fibrils and type VII collagen

The ontogeny and composition of the dermal-epidermal junction (DEJ) in developing human embryonic and fetal skin was studied at progressive stages of gestation by immunofluorescence microscopy and immunocytochemistry using transmission electron microscopy (TEM). The DEJ of embryonic skin at 5 weeks estimated gestational age (EGA) was a simple basement membrane zone limited to the basal cell plasma membrane, lamina lucida, and lamina densa. A network of reticular collagen fibrils (reticular lamina) was deposited beneath the lamina densa by 6 weeks. Coincident with the onset of increased complexity in epidermal and dermal structure, at the time of the embryonic to fetal transition, the DEJ displayed additional components that were markers of maturation. At 7-8 weeks EGA, fine filamentous structures extended from the DEJ into the reticular lamina. By 9 weeks EGA hemidesmosomes and banded anchoring fibrils were recognizable, although distributed sparsely at the DEJ. With increasing gestational age, these structures displayed greater electron density and structural completeness. By the end of the first trimester, the DEJ appeared ultrastructurally similar to that of mature skin. Weak immunofluorescent labeling demonstrated the presence of type VII collagen at the DEJ by 8 weeks EGA. From 10-12 weeks EGA immunofluorescent labeling of the DEJ for type VII collagen was distinctly punctate, while immunoperoxidase labeling observed by TEM was linear, continuous, and sublamina densa in position. With ongoing gestation the immunofluorescent labeling became increasingly stronger at the DEJ. Thus, type VII collagen was present at the DEJ in the zone immediately beneath the lamina densa, before the appearance of mature anchoring fibrils but coordinate with the appearance of fine filamentous, unbanded structures, and appeared to increase with the development and accumulation of anchoring fibrils.