Ahmed, Zeshan

Frontotemporal lobar degeneration with ubiquitin immunoreactive inclusions (FTLD‐U) is the most common cause of frontal lobe dementia. Recently, the TAR DNA binding protein (TDP‐43) has been described as a marker for FTLD‐U. TDP‐43 has been reported to be specific for neuronal inclusions in FTLD‐U and not other degenerative disorders such as Alzheimer's disease (AD). The reported specificity of TDP‐43 makes it possible to detect FTLD‐U in the setting of other neurodegenerative diseases. On this assumption, we determined the frequency of FTLD‐U in AD. Additionally, since FTLD‐U is often associated with hippocampal sclerosis (HpScl), a process characterized by neuronal loss in Sommer's sector of the hippocampus, we also determined the frequency of FTLD‐U in HpScl. A series of 74 AD and 20 HpScl cases were screened with TDP‐43 immunohistochemistry. Immunoreactivity for TDP‐43 was detected in 13 of 20 (65%) HpScl cases and 42 of 74 (57%) AD cases, including 33 of 44 (75%) cases of AD with HpScl and 9 of 30 (30%) cases of AD without HpScl. The specificity of TDP‐43 was assessed by double immunolabeling for tau at the light and electron microscopic level. The frequency of tau and TDP‐43 co‐localization was 13%. At the EM level TDP‐43 immunoreactivity was present in cytosolic granular material, but some tau‐positive filaments were also labeled. The results suggest that FTLD‐U occurs frequently in HpScl and AD.

Coronin‐1a is an evolutionarily conserved protein involved in rearrangements of the actin cytoskeleton. The expression of coronin‐1a is restricted to cells of the hematopoietic lineage. Microglia are resident immune cells of the central nervous system thought to have hematopoietic origins. The aim of this study was to determine if coronin‐1a could be used as a marker for detecting microglia in mammalian species. Using a polyclonal antibody and immunohistochemistry, we show that coronin‐1a is an effective marker for microglia in tissue culture and archival formalin fixed, paraffin embedded tissue, including a range of neurodegenerative and neuroinflammatory conditions and transgenic mice. In human, monkey, horse, rat and mouse tissue coronin‐1a immunoreactivity was present in cells with the morphology and distribution of microglia, even in sections that had been stored for long periods of time. The identity of coronin‐1a positive cells as microglia was confirmed with double immunolabeling for HLA‐DR and Iba‐1. Coronin‐1a immunoreactivity was also detected in T‐ and B‐lymphocytes in lymphoid tissue and neuroinflammatory conditions, but it was not expressed by astrocytes or oligodendrocytes. The results demonstrate that coronin‐1a is a novel marker for microglia in routinely processed tissue from normal and neurodegenerative conditions in both humans and animals.

ABSTRACT Globoid cell leukodystrophy (GLD), also known as Krabbe disease, is a devastating, degenerative neurological disorder. It is inherited as an autosomal recessive trait caused by loss‐of‐function mutations in the galactocerebrosidase (GALC) gene. Previously, we have shown that peripheral injection of recombinant GALC, administered every other day, results in a substantial improvement in early clinical phenotype in the twitcher mouse model of GLD. While we did detect active enzyme in the brain following peripheral administration, most of the administered enzyme was localized to the periphery. Given the substantial central nervous system (CNS) involvement in this disease, we were interested in determining whether or not a single‐dose administration of the recombinant enzyme directly to the CNS, which could potentially be achieved clinically, would result in any substantial improvement. Following intracerebroventricu‐lar (icv) administration of GALC we noted a significant, 16.5%, reduction in the GALC substrate psychosine, the abnormal accumulation of which is believed to play a pivotal role in the CNS pathology observed in this disease. Moreover, recombinant GALC was found not only in periventricular regions but also at sites distant to the injection such as the cerebral cortex and cerebellum. Most importantly, animals receiving a single icv dose of the enzyme at postnatal day 20 survived up to 51 days, which compares favorably to the control twitcher animals, which normally only live to postnatal day 40/42. These results indicate that even a single icv administration of the recombinant enzyme can have significant clinical impact and suggests that other lysosomal storage disorders with significant CNS involvement may similarly benefit.—Lee, W.C., Tsoi, Y.K., Troendle, F.J., DeLucia, M.W., Ahmed, Z., Dicky, C.A., Dickson, D.W., Eckman, C.B. Single dose intracerebroventricular administration of galactocerebrosidase improves survival in a mouse model of globoid cell leukodystrophy. FASEB J. 21, 2520–2527 (2007)

This study identifies the actin-binding protein, coronin-1a, as a novel and effective immunohistochemical marker for microglia in both cell cultures and in formaldehyde-fixed, paraffin-embedded tissue. Antibodies to coronin-1a effectively immunostained microglia in human, monkey, horse, rat, and mouse tissues, even in tissues stored for long periods of time. The identity of coronin-1a-immunoreactive cells as microglia was confirmed using double immunolabeling with cell type-specific markers as well as by morphological features and the distribution of immunoreactive cells. These properties are shared by another actin-binding protein, IBA-1. Unlike IBA-1, coronin-1a immunoreactivity was also detected in lymphocytes and certain other hematopoietic cells. The results indicate that both coronin-1a and IBA-1 are robust markers for microglia that can be used in routinely processed tissue of humans and animals. Because both coronin-1a and IBA-1 are actin-binding proteins that play a role in rearrangement of the membrane cytoskeleton, it suggests that these proteins are critical to dynamic properties of microglia.