Brain progranulin expression in GRN-associated frontotemporal lobar degeneration

• Published in: Acta neuropathologica Vol. 119; no. 1; pp. 111 - 122
• Main Authors: Chen-Plotkin, Alice S., Xiao, Jiping, Geser, Felix, Martinez-Lage, Maria, Grossman, Murray, Unger, Travis, Wood, Elisabeth M., Van Deerlin, Vivianna M., Trojanowski, John Q., Lee, Virginia M.-Y.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.01.2010; Springer Nature B.V
• Subjects: Alleles; Autopsies; Brain - metabolism; Brain research; Cerebellum - metabolism; Dementia; DNA-Binding Proteins - metabolism; Enzyme-Linked Immunosorbent Assay; Executive function; Frontal Lobe - metabolism; Frontotemporal Lobar Degeneration - blood; Frontotemporal Lobar Degeneration - genetics; Frontotemporal Lobar Degeneration - metabolism; Genetic Variation; Humans; Immunoblotting; Immunohistochemistry; Intercellular Signaling Peptides and Proteins - blood; Intercellular Signaling Peptides and Proteins - genetics; Intercellular Signaling Peptides and Proteins - metabolism; Medicine; Medicine & Public Health; Microglia - metabolism; Mutation; Neurosciences; Occipital Lobe - metabolism; Original Paper; Pathology; Peptides; Proteins; RNA, Messenger - metabolism; Sequence Analysis, DNA; Temporal Lobe - metabolism; Frontotemporal lobar degeneration; Progranulin; Frontotemporal dementia; TDP-43; Microglia
• ISSN: 0001-6322; 1432-0533
• DOI: 10.1007/s00401-009-0576-2

Frontotemporal lobar degeneration with TDP-43 inclusions (FTLD-TDP) is characterized by progressive decline in behavior, executive function, and language. Progranulin ( GRN ) gene mutations are pathogenic for FTLD-TDP, and GRN transcript haploinsufficiency is the proposed disease mechanism. However, the evidence for this hypothesis comes mainly from blood-derived cells; we measured progranulin expression in brain. We characterized mRNA and protein levels of progranulin from four brain regions (frontal cortex, temporal cortex, occipital cortex, and cerebellum) in FTLD-TDP patients with and without GRN mutations, as well as neurologically normal individuals. Moreover, we performed immunohistochemistry to evaluate the degree of TDP-43 pathology and microglial infiltration present in these groups. In most brain regions, patients with GRN mutations showed mRNA levels comparable to normal controls and to FTLD-TDP without GRN mutations. However, GRN transcript levels in a brain region severely affected by disease (frontal cortex) were increased in mutation-bearing patients. When compared with normal individuals, GRN mutation-bearing cases had a significant reduction in the amount of progranulin protein in the cerebellum and occipital cortex, but not in the frontal and temporal cortices. In GRN mutant cases, GRN mRNA originated from the normal allele, and moderate microglial infiltration was observed. In conclusion, GRN mutation carriers have increased levels of mRNA transcript from the normal allele in brain, and proliferation of microglia likely increases progranulin levels in affected regions of the FTLD-TDP brain, and whether or not these findings underlie the accumulation of TDP-43 pathology in FTLD-TDP linked to GRN mutations remains to be determined.