Showing papers by "John Q. Trojanowski published in 1987"

Two-stage expression of neurofilament polypeptides during rat neurogenesis with early establishment of adult phosphorylation patterns

Abstract: Monoclonal antibodies (mAbs) to rat neurofilament (NF) proteins NF-L, NF-M, and NF-H were used to examine the developmental programs of NF expression in rat embryos. The ability of these mAbs to recognize differentially phosphorylated states of NF-M and NF-H (Lee et al., 1987, the preceding paper) was exploited in order to examine the temporal and spatial patterns of NF phosphorylation during early neuronal development in vivo. NF proteins were first detected on the twelfth day postfertilization (E12) using NF-L- or NF-M-specific mAbs. By E13, the coexpression of NF-L and NF-M was widespread, reflecting dramatic increases of immunoreactivity to both subunits. Partial phosphorylation, denoted P[+], of NF-M was already present in perikarya and neurites of E12 neurons. Extensively phosphorylated, or P[+++], isoforms of NF-M appeared in E13 axons, thereby establishing a proximodistal gradient of NF phosphorylation during the earliest phase of NF expression. Immunoblots of tissue homogenates revealed that most NF-M of E13 embryos exists in a partially phosphorylated, or P[+], isoform. Unequivocal staining for NF-H first appeared at E15, a time at which NF-L and NF-M had already attained their adult patterns of immunocytochemical staining. Levels of NF-H were extremely low at E15 but could be detected in all of its differentially phosphorylated states, i.e., nonphosphorylated P[-], partly P[+], and highly P[+++] phosphorylated isoforms. P[+++] isoforms of NF-H were restricted to the distal portions of E15 axons, although staining of more proximal axons, like those in adult, was noted by E17. Immunoblots of E17 embryos revealed most NF-H as P[-] and P[+] isoforms. Quantities of immunoreactive NF-H increased very slowly and remained well below those of NF-M and NF-L for several weeks beyond birth. These results show that sequential forms of NFs are expressed by developing and maturing neurons throughout the nervous system. An "immature" form of NFs, composed of NF-M and NF-L, appears to function in establishing the neuronal phenotype and in initiating and maintaining neurite outgrowth. Addition of NF-H confers a "mature" state to the NF. This delayed expression of NF-H is a slow and graduated process that coincides in time with the stabilization of neuronal circuitries and may be important in modulating axonal events, such as the slowing of cytoskeletal transport and the growth of axonal caliber.

Monoclonal antibodies distinguish several differentially phosphorylated states of the two largest rat neurofilament subunits (NF-H and NF-M) and demonstrate their existence in the normal nervous system of adult rats.

Abstract: A new panel of greater than 300 monoclonal antibodies (mAbs) was prepared to the high, middle, and low Mr rat neurofilament (NF) subunits (NF-H, NF-M and NF-L, respectively). NF proteins were purified both from native, i.e., phosphorylated rat NFs and from enzymatically dephosphorylated rat NFs. The resulting mAbs were used to biochemically and immunochemically distinguish and characterize distinct and differentially phosphorylated isoforms of NF subunits. By immunoblot, all mAbs specific for NF-L and some mAbs specific for NF-M detected their specific NF subunit regardless of whether or not the NFs had been treated with alkaline phosphatase, and such antibodies were termed “phosphate-independent” or P[ind] mAbs. The other mAbs were specific for NF-M, NF-H, or for both NF-M and NF-H, and they recognized epitopes in the COOH termini of these subunits. Significantly, the latter mAbs could discriminate different isoforms of NF-M and NF-H, depending on the phosphorylation state of each variant. Such mAbs were assigned to one of 4 distinct categories on the basis of their performance in immunoblots of progressively dephosphorylated rat NF samples and by immunohistochemistry of various adult rat nervous tissues: (1) P[-] mAbs preferentially stained neuronal perikarya and dendrites, and they recognized only extensively dephosphorylated (and nonphosphorylated) NF- H; (2) P[+] mAbs stained axons more strongly than perikarya, and primarily blotted phosphorylated, but not nonphosphorylated, forms of NF-H and NF-M; (3) P[++] mAbs stained axons almost to the exclusion of perikarya, and in blots recognized only the extensively phosphorylated forms of NF-H and NF-M (i.e., subunits subjected to limited enzymatic dephosphorylation); (4) P[ ] mAbs also predominantly stained axons, but the briefest alkaline phosphatase treatment abolished the NF-M and NF-H immunobands produced by these mAbs. Two-dimensional gel analysis and immunoblotting of total proteins from adult rat dorsal root ganglion verified mAb specificity in situ, and showed that differentially phosphorylated isoforms of NF-M and NF-H occur in vivo. This provided additional evidence that mAbs can detect all 4 phosphorylation- dependent endogenous isoelectric variants of NF-H and NF-M.(ABSTRACT TRUNCATED AT 400 WORDS)

Does chondroid chordoma exist

Abstract: The existence of chondroid chordoma (CC), initially described in 1973, has remained controversial. Since the antigenic profiles of both chordoma (CD) and cartilaginous (chondroid) lesions have been well characterized, we decided to study chondroid chordoma immunohistochemically. Our hypothesis was that chondroid chordoma should display a hybrid or mixed pattern of staining: chordomatous areas with an epithelial phenotype and cartilaginous areas with a mesenchymal (non-epithelial) phenotype. An analysis of CC (seven cases) was performed and compared with results obtained on notochord, cartilage, classic CD (18 cases), peripheral chondromas (two cases), and peripheral chondrosarcomas (CS, eight cases). Four epithelial markers were employed: MKER and AE-1 (both monoclonal antibodies to cytokeratin); PKER (a polyclonal antibody to cytokeratin); and, EMA (epithelial membrane antigen). In addition, selected cases were tested for the presence of neurofilament (NF) and glial fibrillary acidic protein (GFAP). All 18 CD's exhibited the expected epithelial immunophenotype — MKER+, AE-1+, PKER+, and EMA+ — a reaction pattern nearly identical to that found in fetal notochord. This reinforced the importance of the growth pattern in assessing the presence of chordomatous elements. All chondromas and CS's failed to express any of the epithelial markers studied and contained only S-100 immunoreactivity, like cartilage. Chondroid chordoma resembled cartilaginous tumors immunohistochemically; no mixed pattern with even focal epithelial marker reactivity was identified. All CC tested were also NF and GFAP negative. We conclude that CC either does not exist or is extremely rare and that these tumors are cartilaginous in nature. We propose abandoning the term chondroid chordoma and replacing it with “low grade chondrosarcoma”. Distinction from CD is still imperative due to the clear difference in natural history; we provide histological definitions and an immunophenotype to aid in this distinction.

A rapidly dividing human medulloblastoma cell line (D283 MED) expresses all three neurofilament subunits.

Abstract: The majority of cells in a rapidly dividing human medulloblastoma cell line (D283 MED) are shown to express the two high-molecular-weight human neurofilament (NF) subunits, whereas a minority express the low-molecular-weight NF subunit. These three polypeptides are integral subunits of the intermediate filaments (IFs) found in normal neurons. Other cell type-specific IF proteins (keratin, desmin, and glial filament polypeptides) are not present in D283 MED cells. Further, the immunocytochemical, immunochemical and ultrastructural data suggest that the neurofilaments in these cells are abnormal, possibly because of a paucity of the low-molecular-weight NF subunit. This is the first human cell line derived from a central nervous system tumor that is capable of expressing all three NF triplet proteins. It is a unique model system for studies of normal and abnormal human NF metabolism as well as for probing the cell biology of medulloblastomas.

Neurofilament proteins and human nervous system tumors.

Abstract: Neoplasms that arise in the peripheral (e.g., carotid body tumors, neuroblastomas, pheochromocytomas) or central (gangliocytomas, medulloblastomas) nervous system express a number of neuron-specific gene products. Presumably, these tumors are derived from precursor cells that are or have the potential to develop into neurons or neuron-like cells. This report provides a critical examination of the hypothesis that cytoskeletal proteins of normal neurons, in particular the neuron-specific class of intermediate filaments (neurofilaments), are present but are abnormal in neoplasms derived from neurons or neuron-like cells. The implications of these findings for understanding tumor promotion and progression, and for development of molecular probes for the diagnostic assessment of these neoplasms, are discussed.