Mutation in the key enzyme of sialic acid biosynthesis causes severe glomerular proteinuria and is rescued by N-acetylmannosamine.
Mutations in the key enzyme of sialic acid biosynthesis, uridine diphospho-N-acetylglucosamine 2-epimerase/N-acetylmannosamine (ManNAc) kinase (GNE/MNK), result in hereditary inclusion body myopathy (HIBM), an adult-onset, progressive neuromuscular disorder. We created knockin mice harboring the M712T Gne/Mnk mutation. Homozygous mutant (Gne(M712T/M712T)) mice did not survive beyond P3. At P2, significantly decreased Gne-epimerase activity was observed in Gne(M712T/M712T) muscle, but no myopathic features were apparent. Rather, homozygous mutant mice had glomerular hematuria, proteinuria, and podocytopathy. Renal findings included segmental splitting of the glomerular basement membrane, effacement of podocyte foot processes, and reduced sialylation of the major podocyte sialoprotein, podocalyxin. ManNAc administration yielded survival beyond P3 in 43% of the Gne(M712T/M712T) pups. Survivors exhibited improved renal histology, increased sialylation of podocalyxin, and increased Gne/Mnk protein expression and Gne-epimerase activities. These findings establish this Gne(M712T/M712T) knockin mouse as what we believe to be the first genetic model of podocyte injury and segmental glomerular basement membrane splitting due to hyposialylation. The results also support evaluation of ManNAc as a treatment not only for HIBM but also for renal disorders involving proteinuria and hematuria due to podocytopathy and/or segmental splitting of the glomerular basement membrane.
Galeano
Belinda
B
Medical Genetics Branch, National Human Genome Research Institute, NIH, Bethesda, Maryland 208921851, USA.
Klootwijk
Riko
R
Manoli
Irini
I
Sun
MaoSen
M
Ciccone
Carla
C
Darvish
Daniel
D
Starost
Matthew F
MF
Zerfas
Patricia M
PM
Hoffmann
Victoria J
VJ
Hoogstraten-Miller
Shelley
S
Krasnewich
Donna M
DM
Gahl
William A
WA
Huizing
Marjan
M
D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D004195:Disease Models, Animal; D005260:Female; D006595:Hexosamines / Q000627:therapeutic use*; D006801:Humans; D007674:Kidney Diseases / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism*; D007678:Kidney Glomerulus / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D008854:Microscopy, Electron; D008954:Models, Biological; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism; D019158:N-Acetylneuraminic Acid / Q000096:biosynthesis*; D011247:Pregnancy; D011507:Proteinuria / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism*
D017931:DNA Primers; D006595:Hexosamines; D009097:Multienzyme Complexes; C482901:UDP-N-acetylglucosamine 2-epimerase - N-acetylmannosamine kinase; D019158:N-Acetylneuraminic Acid; C002022:N-acetylmannosamine