Development of Cat-301 immunoreactivity in auditory brainstem nuclei of the gerbil.

The developing brainstem auditory system has been studied in detail by using anatomical and physiological techniques. However, it is not known whether immature auditory neurons exhibit different molecular characteristics than those of physiologically mature neurons. To address this issue, we examined the distribution of Cat-301 immunoreactivity in the developing auditory brainstem of gerbils. Cat-301 is a monoclonal antibody that recognizes a 680-kD chondroitin sulfate proteoglycan similar to aggrecan, a high-molecular-weight chondroitin sulfate proteoglycan found in cartilage. In the central nervous system, Cat-301 immunoreactivity is localized to the extrasynaptic surface of neurons. It has been hypothesized by Hockfield and co-workers (Hockfield et al. [1990a]Cold Spring Harbor Symp. Quart. Biol. 55:504-514) that the Cat-301 proteoglycan is a molecular marker indicating that a neuron has acquired mature neuronal properties. In the current study, Cat-301 staining is first seen at 7 days after birth in the anterior ventral cochlear nucleus (AVCN), the posterior VCN (PVCN), and the medial nucleus of the trapezoid body (MNTB) shortly before the onset of sound-evoked activity. By 21 days after birth, neurons in the AVCN, the PVCN, and the lateral and medial superior olive have attained adult-like distributions of Cat-301 staining concomitant with the physiological maturation of these neurons. Neurons in MNTB attain adult-like distributions of Cat-301 immunoreactivity at 1 year. The maturation of Cat-301 immunoreactivity parallels the physiological maturation of gerbil auditory neurons, and the Cat-301 proteoglycan may play a role in the formation and/or stabilization of auditory synapses.

Monoclonal antibodies distinguish antigenically discrete neuronal types in the vertebrate central nervous system.

Eight hundred hybridoma lines were generated from mice immunized with the fixed gray matter of cat spinal cord. Of these lines, 47 were positive when screened immunohistochemically against sections of the cat spinal cord. Twenty-nine lines secreted antibodies that bound to neuronal antigens. Of these, 16 bound to axons only, 8 bound to axons and cell bodies, and 5 bound to cell bodies only. Eighteen lines secreted antibodies that bound to glial cells. Five lines that secreted antibodies that intensely stained spinal cord sections were cloned and screened against other parts of the central nervous system. Each of these five antibodies bound to specific subsets of neurons. For example, in the spinal cord, one antibody (Cat-301) recognized a surface determinant on the dendrites and cell bodies of neurons that, in morphology and location, resemble long-distance projection neurons. A second antibody (Cat-201) recognized an antigen in axons and in the cytoplasm of neuronal cell bodies that may be a subset of those recognized by Cat-301. A third antibody (Cat-101) recognized only axons. The subcellular localization of the antigen recognized by each antibody is the same in all areas of the central nervous system we have examined. The fact that each of the antibodies described here has a restricted distribution in the central nervous system shows that there is a high degree of molecular diversity among vertebrate neurons and that hybridoma technology can be used to explore this diversity. This class of reagents should be a useful addition to the many established techniques for studying the organization of the vertebrate central nervous system.