Macrophage-colony stimulating factor (M-CSF) enhances proteinuria and recruitment of macrophages into the glomerulus in experimental murine nephritis

In this study, we examined the effects of macrophage-colony stimulating factor (M-CSF) on glomerular macrophages in lipopolysaccharide (LPS)-induced murine nephritis. Mice injected intraperitoneally with either M-CSF plus LPS, LPS alone, M-CSF alone or saline every day for 8 days were examined for the degree of urine albumin excretion and lymphocyte-function associated antigen-1-positive (LFA-1+) cells in peripheral blood as well as renal pathology. From our results, LPS or M-CSF combined with LPS emphasized the degree of proteinuria, glomerular deposition of immunoglobulins and mesangial proliferation, associated with accumulation of macrophages in the glomeruli. However, in immunohistological examination of kidneys from these nephritic mice, neither intercellular adhesion molecule-1 (ICAM-1), which may play an important role in the recruitment of macrophages into glomeruli, M-CSF receptor nor the number of LFA-1+ cells in peripheral blood was enhanced by M-CSF. On the other hand, M-CSF alone induced neither proteinuria nor any pathological changes and did not increase the number of glomerular Mac-1+ cells above that in saline-treated controls. These results indicate that M-CSF does not directly cause glomerulonephritis but might participate in accelerating the glomerular inflammatory process by stimulating a potent chemoattractant to recruit monocytes-macrophages into the glomeruli

X-linked alport syndrome caused by splicing mutations in COL4A5

BACKGROUND AND OBJECTIVES: X-linked Alport syndrome is caused by mutations in the COL4A5 gene. Although many COL4A5 mutations have been detected, the mutation detection rate has been unsatisfactory. Some men with X-linked Alport syndrome show a relatively mild phenotype, but molecular basis investigations have rarely been conducted to clarify the underlying mechanism. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: In total, 152 patients with X-linked Alport syndrome who were suspected of having Alport syndrome through clinical and pathologic investigations and referred to the hospital for mutational analysis between January of 2006 and January of 2013 were genetically diagnosed. Among those patients, 22 patients had suspected splice site mutations. Transcripts are routinely examined when suspected splice site mutations for abnormal transcripts are detected; 11 of them showed expected exon skipping, but others showed aberrant splicing patterns. The mutation detection strategy had two steps: (1) genomic DNA analysis using PCR and direct sequencing and (2) mRNA analysis using RT-PCR to detect RNA processing abnormalities. RESULTS: Six splicing consensus site mutations resulting in aberrant splicing patterns, one exonic mutation leading to exon skipping, and four deep intronic mutations producing cryptic splice site activation were identified. Interestingly, one case produced a cryptic splice site with a single nucleotide substitution in the deep intron that led to intronic exonization containing a stop codon; however, the patient showed a clearly milder phenotype for X-linked Alport syndrome in men with a truncating mutation. mRNA extracted from the kidney showed both normal and abnormal transcripts, with the normal transcript resulting in the milder phenotype. This novel mechanism leads to mild clinical characteristics. CONCLUSIONS: This report highlights the importance of analyzing transcripts to enhance the mutation detection rate and provides insight into genotype-phenotype correlations. This approach can clarify the cause of atypically mild phenotypes in X-linked Alport syndrome