Biallelic variants/mutations of IL1RAP in patients with steroid-sensitive nephrotic syndrome.

Nephrotic syndrome (NS) is a renal disease characterized by severe proteinuria and hypoproteinemia. Although several single-gene mutations have been associated with steroid-resistant NS, causative genes for steroid-sensitive NS (SSNS) have not been clarified. While seeking to identify causative genes associated with SSNS by whole-exome sequencing, we found compound heterozygous variants/mutations (c.524T>C; p.I175T and c.662G>A; p.R221H) of the interleukin-1 receptor accessory protein (IL1RAP) gene in two siblings with SSNS. The siblings' parents are healthy, and each parent carries a different heterozygous IL1RAP variant/mutation. Since IL1RAP is a critical subunit of the functional interleukin-1 receptor (IL-1R), we investigated the effect of these variants on IL-1R subunit function. When stimulated with IL-1ß, peripheral blood mononuclear cells from the siblings with SSNS produced markedly lower levels of cytokines compared with cells from healthy family members. Moreover, IL-1R with a variant IL1RAP subunit, reconstituted on a hematopoietic cell line, had impaired binding ability and low reactivity to IL-1ß. Thus, the amino acid substitutions in IL1RAP found in these NS patients are dysfunctional variants/mutations. Furthermore, in the kidney of Il1rap-/- mice, the number of myeloid-derived suppressor cells, which require IL-1ß for their differentiation, was markedly reduced although these mice did not show significantly increased proteinuria in acute nephrotic injury with lipopolysaccharide treatment. Together, these results identify two IL1RAP variants/mutations in humans for the first time and suggest that IL1RAP might be a causative gene for familial NS.

Positive renal familial history in IgA nephropathy is associated with worse renal outcomes: a single-center longitudinal study.

BACKGROUND: IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. Although most IgAN cases are sporadic, few show a familial aggregation. However, the prevalence and prognosis of IgAN individuals with positive familial history (FH) of renal disorders remains uncertain. To address these issues, we conducted a longitudinal observational study on a single-institution cohort of patients with biopsy-proven IgAN. METHODS: A total of 467 IgAN patients who underwent renal biopsy during 1994 to 2019 were ascertained to have positive- or negative-FH by history taking and were followed for an average of 8.9 years. We compared the clinical and pathological features of the two subgroups. The primary outcome, a composite of a hard endpoint (end-stage renal disease [ESRD]) and surrogate endpoint (a 50% or more reduction in the estimated glomerular filtration rate [eGFR] from baseline), was evaluated. To estimate the risk for progression to ESRD, a Cox proportional hazards analysis was performed for a subset of patients who underwent follow-up for > 2 years and had an eGFR > 30 mL/min/1.73 m2 at baseline (n = 389; observation, 8.7 years). RESULTS: Positive-FH subtype accounted for 11.6% (n = 54) of all IgAN patients. At baseline, there were no significant differences between the positive- and negative-FH subgroups regarding age, sex, comorbid disease, MEST-C score, observation period, and therapeutic interventions. However, the eGFR value at baselines was significantly lower in the positive-FH subgroup than in the negative-FH subgroup (P < 0.01). On multivariate analysis, positive-FH emerged an independent determinant of poorer renal outcomes (odds ratio, 2.31; 95% confidence interval, 1.10-4.85; P = 0.03), after adjusting for confounding factors. eGFR at follow-up was significantly lower in the positive-FH subgroup than in the negative-FH subgroup after adjustment for age and observation period. CONCLUSIONS: Positive-FH was found in 11.6% of all IgAN patients, consistent with the incidence seen in previous literature. A significantly lower eGFR at baseline and last follow-up and unfavorable renal outcomes in the positive-FH subgroup suggest that certain genetic risk factors predisposing to renal failure may exist in a fraction of our IgAN cohort. (331 words).

Transcription factor MafB in podocytes protects against the development of focal segmental glomerulosclerosis.

Focal segmental glomerulosclerosis (FSGS) is a common cause of steroid-resistant nephrotic syndrome. Spontaneous remission of FSGS is rare and steroid-resistant FSGS frequently progresses to renal failure. Many inheritable forms of FSGS have been described, caused by mutations in proteins that are important for podocyte function. Here, we show that a basic leucine zipper transcription factor, MafB, protects against FSGS. MAFB expression was found to be decreased in the podocytes of patients with FSGS. Moreover, conditional podocyte-specific MafB-knockout mice developed FSGS with massive proteinuria accompanied by depletion of the slit diaphragm-related proteins (Nphs1 and Magi2), and the podocyte-specific transcription factor Tcf21. These findings indicate that MafB plays a crucial role in the pathogenesis of FSGS. Consistent with this, adriamycin-induced FSGS and attendant proteinuria were ameliorated by MafB overexpression in the podocytes of MafB podocyte-specific transgenic mice. Thus, MafB could be a new therapeutic target for FSGS.

Immune-complex glomerulonephritis with a membranoproliferative pattern in Frasier syndrome: a case report and review of the literature.

BACKGROUND: Mutations in the Wilms tumor 1 gene cause a spectrum of podocytopathy ranging from diffuse mesangial sclerosis to focal segmental glomerulosclerosis. In a considerable fraction of patients with Wilms tumor 1 mutations, the distinctive histology of immune-complex-type glomerulonephritis has been reported. However, the clinical relevance and etiologic mechanisms remain unknown. CASE PRESENTATION: A 5-year-old child presented with steroid-resistant nephrotic range proteinuria. Initial renal biopsy revealed predominant diffuse mesangial proliferation with a double-contour and coexisting milder changes of focal segmental glomerulosclerosis. Immunofluorescence and electron microscopy revealed a full-house-pattern deposition of immune complexes in the subendothelial and paramesangial areas. Serial biopsies at 6 and 8 years of age revealed that more remarkable changes of focal segmental glomerulosclerosis had developed on top of the initial proliferative glomerulonephritis. Identification of a de novo Wilms tumor 1 splice donor-site mutation in intron 9 (NM_024426.6:c.1447 + 4C > T) and 46,XY-gonadal dysgenesis led to the diagnosis of Frasier syndrome. CONCLUSIONS: Our findings, together with those of others, point to the importance of heterogeneity in clinicopathological phenotypes caused by Wilms tumor 1 mutations and suggest that immune-complex-mediated membranoproliferative glomerulopathy should be considered as a histological variant.

Homozygous splicing mutation in NUP133 causes Galloway-Mowat syndrome.

OBJECTIVE: Galloway-Mowat syndrome (GAMOS) is a neural and renal disorder, characterized by microcephaly, brain anomalies, and early onset nephrotic syndrome. Biallelic mutations in WDR73 and the 4 subunit genes of the KEOPS complex are reported to cause GAMOS. Furthermore, an identical homozygous NUP107 (nucleoporin 107kDa) mutation was identified in 4 GAMOS-like families, although biallelic NUP107 mutations were originally identified in steroid-resistant nephrotic syndrome. NUP107 and NUP133 (nucleoporin 133kDa) are interacting subunits of the nuclear pore complex in the nuclear envelope during interphase, and these proteins are also involved in centrosome positioning and spindle assembly during mitosis. METHODS: Linkage analysis and whole exome sequencing were performed in a previously reported GAMOS family with brain atrophy and steroid-resistant nephrotic syndrome. RESULTS: We identified a homozygous NUP133 mutation, c.3335-11T>A, which results in the insertion of 9bp of intronic sequence between exons 25 and 26 in the mutant transcript. NUP133 and NUP107 interaction was impaired by the NUP133 mutation based on an immunoprecipitation assay. Importantly, focal cortical dysplasia type IIa was recognized in the brain of an autopsied patient and focal segmental glomerulosclerosis was confirmed in the kidneys of the 3 examined patients. A nup133-knockdown zebrafish model exhibited microcephaly, fewer neuronal cells, underdeveloped glomeruli, and fusion of the foot processes of the podocytes, which mimicked human GAMOS features. nup133 morphants could be rescued by human wild-type NUP133 mRNA but not by mutant mRNA. INTERPRETATION: These data indicate that the biallelic NUP133 loss-of-function mutation causes GAMOS. Ann Neurol 2018;84:814-828.

A mutation in transcription factor MAFB causes Focal Segmental Glomerulosclerosis with Duane Retraction Syndrome.

Focal segmental glomerulosclerosis (FSGS) is a leading cause of end-stage renal disease in children and adults. Genetic factors significantly contribute to early-onset FSGS, but the etiologies of most adult cases remain unknown. Genetic studies of monogenic syndromic FSGS exhibiting extra-renal manifestations have uncovered an unexpected biological role for genes in the development of both podocytes and other cellular lineages. To help define these roles, we studied two unrelated families with FSGS associated with Duane Retraction Syndrome, characterized by impaired horizontal eye movement due to cranial nerve malformation. All four affected individuals developed FSGS and Duane Retraction Syndrome in their first to second decade of life, manifested as restricted abduction together with globe retraction and narrowed palpebral fissure on attempted adduction. Hypoplasia of the abducens nerves and hearing impairment occurred in severely affected individuals. Genetic analyses revealed that affected individuals harbor a rare heterozygous substitution (p.Leu239Pro) in MAFB, a leucine zipper transcription factor. Luciferase assays with cultured monocytes indicated that the substitution significantly reduced transactivation of the F4/80 promoter, the known MAFB recognition element. Additionally, immunohistochemistry indicated reduced MAFB expression in the podocytes of patients. Structural modeling suggested that the p.Leu239Pro substitution in the DNA-binding domain possibly interferes with the stability of the adjacent zinc finger. Lastly, podocytes in neonatal mice with p.Leu239Pro displayed impaired differentiation. Thus, MAFB mutations impair development and/or maintenance of podocytes, abducens neurons and the inner ear. The interactions between MAFB and regulatory elements in these developing organs are likely highly specific based on spatiotemporal requirements.

Biallelic Mutations in Nuclear Pore Complex Subunit NUP107 Cause Early-Childhood-Onset Steroid-Resistant Nephrotic Syndrome.

The nuclear pore complex (NPC) is a huge protein complex embedded in the nuclear envelope. It has central functions in nucleocytoplasmic transport, nuclear framework, and gene regulation. Nucleoporin 107 kDa (NUP107) is a component of the NPC central scaffold and is an essential protein in all eukaryotic cells. Here, we report on biallelic NUP107 mutations in nine affected individuals who are from five unrelated families and show early-onset steroid-resistant nephrotic syndrome (SRNS). These individuals have pathologically focal segmental glomerulosclerosis, a condition that leads to end-stage renal disease with high frequency. NUP107 is ubiquitously expressed, including in glomerular podocytes. Three of four NUP107 mutations detected in the affected individuals hamper NUP107 binding to NUP133 (nucleoporin 133 kDa) and NUP107 incorporation into NPCs in vitro. Zebrafish with nup107 knockdown generated by morpholino oligonucleotides displayed hypoplastic glomerulus structures and abnormal podocyte foot processes, thereby mimicking the pathological changes seen in the kidneys of the SRNS individuals with NUP107 mutations. Considering the unique properties of the podocyte (highly differentiated foot-process architecture and slit membrane and the inability to regenerate), we propose a "podocyte-injury model" as the pathomechanism for SRNS due to biallelic NUP107 mutations.

A familial case of Galloway-Mowat syndrome due to a novel TP53RK mutation: a case report.

BACKGROUND: Galloway-Mowat syndrome (GAMOS) is a rare hereditary renal-neurological disease characterized by early-onset steroid-resistant nephrotic syndrome in combination with microcephaly and brain anomalies. Recently, novel causative mutations for this disease have been identified in the genes encoding the four KEOPS subunits: OSGEP, TP53RK, TPRKB, and LAGE3. CASE PRESENTATION: We detected a novel homozygous TP53RK mutation (NM_033550, c.194A > T, p.Lys65Met) using whole exome sequencing in a familial case of GAMOS with three affected siblings. All three patients manifested similar phenotypes, including very early-onset nephrotic syndrome (8 days, 1 day, and 1 day after birth, respectively), microcephaly, dysmorphic faces, and early fatality (10 months, 21 days, and 25 days of age, respectively). One patient also showed hiatal hernia with gastric volvulus. Renal biopsy performed on one patient revealed focal segmental glomerulosclerosis with severe tubulo-interstitial changes. CONCLUSION: We report on a familial case of GAMOS with three affected siblings carrying a novel homozygous TP53RK mutation. To our knowledge, this is only the second report on GAMOS in association with a TP53RK mutation.

Long-term clinicopathologic observation in a case of steroid-resistant nephrotic syndrome caused by a novel Crumbs homolog 2 mutation.

Recent advances in high-throughput sequencing for clinical genetic testing have revealed novel disease-causing genes, such as Crumbs homolog 2 (CRB2) for early-onset steroid-resistant nephrotic syndrome (SRNS). We report the long-term clinicopathologic observation of a Japanese female patient with SRNS caused by a newly identified compound heterozygous mutation of CRB2 (p.Arg628Cys and p.Gly839Trp located in the 10th and 11th epidermal growth factor-like domains, respectively). She was initially examined during a mass urinary screening for 3.5-year-old children in Japan. Although she developed long-standing SRNS without any extrarenal clinical signs thereafter, her renal function was well-preserved over the next 17 years. In total, six sequential renal biopsy specimens revealed histologic alterations ranging from minor glomerular abnormalities to advanced focal segmental glomerulosclerosis (FSGS). A genetic analysis for SRNS performed at 19 years of age revealed a newly identified compound heterozygous mutation in CRB2. Glomerular CRB2 immunoreactivity in biopsy specimens from the patient was scanty, whereas intense expression was observed in those from patients with idiopathic FSGS or in controls. To our knowledge, this is the first report regarding a long-term outcome in a case of SRNS due to an identified CRB2 mutation. Although the phenotype of CRB2 mutation-related syndrome is now expanding, we believe that this case might provide a novel clinicopathologic aspect of this syndrome.

A Nationwide Survey on Danon Disease in Japan.

Danon disease, an X-linked dominant cardioskeletal myopathy, is caused by primary deficiency of lysosome-associated membrane protein-2 (LAMP-2). To clarify the clinicopathological features and management, we performed the first nationwide, questionnaire-based survey on Danon disease in Japan. A total of 39 patients (17 males, 22 females) from 20 families were identified in the analysis. All patients had cardiomyopathy. Of the 21 patients who died, 20 (95%) died of cardiac failure or sudden cardiac arrest. Most patients had hypertrophic cardiomyopathy. Wolf⁻Parkinson⁻White syndrome was present at a comparatively high incidence (54% in males, 22% in females). Only one female patient received a heart transplant, which is the most effective therapy. Histopathologically, all male patients showed autophagic vacuoles with sarcolemmal features in muscle. Half of the probands showed de novo mutations. Male patients showed completely absent LAMP-2 expression in muscle. In contrast, female patients showed decreased LAMP-2 expression, which is suggested to reflect LAMP-2 haploinsufficiency due to a heterozygous null mutation. In conclusion, Danon disease is an extremely rare muscular disorder in Japan. Cardiomyopathy is the most significant prognostic factor and the main cause of death. Our findings suggest that the present survey can extend our understanding of the clinical features of this rare disease.

NUP107 mutations in children with steroid-resistant nephrotic syndrome.

BACKGROUND: NUP107 is a novel gene associated with autosomal recessive steroid-resistant nephrotic syndrome (SRNS) with focal segmental glomerulosclerosis (FSGS) in children. The frequency of NUP107 mutations in children with SR-FSGS remains unknown. METHODS: Nine families with two siblings affected by childhood-onset SRNS or proteinuria were recruited. FSGS was confirmed by a kidney biopsy in at least one affected sibling in all families. Additionally, 69 sporadic pediatric cases with biopsy-proven SR-FSGS who had not responded to any treatment were included. All coding exons with flanking introns of the NUP107 gene were amplified using polymerase chain reaction and directly sequenced. RESULTS: Biallelic NUP107 mutations were detected in four pairs (44.4%) of siblings from the familial cases and three (4.3%) sporadic cases. All affected patients harbored the p.Asp831Ala mutation in one allele and a truncating or abnormal splicing mutation in the other allele. NUP107 mutation-positive patients showed an earlier onset age (39.4 ± 13.1 versus 76.8 ± 50.0 months, P= 0.027) and more rapid progression to end-stage renal disease (at the ages of 58.9 ± 23.4 versus 123.1 ± 62.7 months, P < 0.001) compared with mutation-negative patients. None of the eight mutation-positive cases, who underwent kidney transplantation, showed recurrence of FSGS in the graft kidney, while 35.3% of mutation-negative cases showed recurrence of FSGS. CONCLUSIONS: An unexpectedly high incidence of NUP107 mutations was observed in Korean children with SR-FSGS. Initial genetic screening of children with SR-FSGS should include the NUP107 gene, at least in Korea. Further studies are necessary to determine the incidences of NUP107 mutations in other countries.

Decreased urinary excretion of the ectodomain form of megalin (A-megalin) in children with OCRL gene mutations.

BACKGROUND: The oculocerebrorenal syndrome of Lowe gene (OCRL) is located on chromosome Xq25-26 and encodes an inositol polyphosphate-5-phosphatase (OCRL-1). Mutations in this gene cause Lowe syndrome (LS) or type 2 Dent disease, of which low-molecular-weight (LMW) proteinuria is a characteristic feature. Megalin is considered to play an important role in the development of renal tubular proteinuria. Two forms of megalin are excreted into the urine: full-length megalin (C-megalin) and megalin ectodomain (A-megalin). We have explored the role of megalin in the development of LMW proteinuria in patients with OCRL mutations by determining urinary megalin fractions. METHODS: We measured A- and C-megalin in spot urine samples from five male patients with OCRL mutations (median age 9 years), using sandwich enzyme-linked immunosorbent assays, and adjusted the obtained values for excreted creatinine. The results were compared with those of 50 control subjects and one patient with type 1 Dent disease (T1D). RESULTS: All patients demonstrated normal levels of urinary C-megalin. However, patients with OCRL mutations or T1D showed abnormally low levels of urinary A-megalin, with the exception of one 5-year-old boy with LS, who was the youngest patient enrolled in the study. CONCLUSIONS: Decreased excretion of urinary A-megalin in four out of five patients with OCRL mutations suggests that LMW proteinuria may be caused by impaired megalin recycling within the proximal tubular cells. Homologous enzymes, similar to inositol polyphosphate-5-phosphatase B in mice, may help to compensate for defective OCRL-1 function during early childhood.

Correlation of whole kidney hypertrophy with glomerular over-filtration in live, gender-mismatched renal transplant allografts.

AIM: Optimizing nephron supply to recipient demand is a non-immunologic determinant of renal allograft outcome. Nephron reduction is usually caused by physical donor-recipient mismatch, but its pathologic relevance remains to be determined. METHODS: Thirty-one recipients of living donor renal transplants were divided into three subgroups: those who received transplants from the same gender (n = 6, Group 1) and those who underwent male-to-female (n = 8, Group 2) and female-to-male (n = 17, Group 3) transplants. Renal mass was evaluated by three-dimensional computed tomography (3D-CT) volumetry before and one year after transplantation. Glomerular volume was determined from protocol biopsies obtained one hour and one year after transplantation. RESULTS: Histologically determined glomerular volume in biopsied tissues showed a significant linear correlation with allograft size on 3D-CT volumetry (P < 0.001, r = 0.625). Mismatches in body weight, glomerular volume and kidney volume ratios were significantly greater in female-to-male (Group 3) than in male-to-female (Group 2) transplants (P < 0.001 each). Despite the two groups having nearly equal graft filtration rates one year after transplantation, proteinuria rate was three-fold higher in Group 3 than in Group 2 (P < 0.001). CONCLUSION: These findings suggest that too small graft size, frequent in female-to-male transplants, could cause hypertrophy in both kidneys and glomeruli, thereby affecting allograft function and survival.

Nephron development and extrarenal features in a child with congenital nephrotic syndrome caused by null LAMB2 mutations.

BACKGROUND: Congenital nephrotic syndrome (CNS) is a rare disorder caused by various structural and developmental defects of glomeruli. It occurs typically as an isolated kidney disorder but associates sometimes with other systemic, extrarenal manifestations. CASE PRESENTATIONS: An infant presented with severe CNS, which progressed rapidly to renal failure at age of 3 months and death at 27 months. The clinical phenotypes and genetic causes were studied, including the renal pathology at autopsy. Besides the CNS, the affected child had remarkable right-side predominant eye-ball hypoplasia with bilateral anterior chamber dysgenesis (microcoria). Brain MRI revealed grossly normal development in the cerebrum, cerebellum, and brain stem. Auditory brainstem responses were bilaterally blunted, suggesting a defective auditory system. At autopsy, both kidneys were mildly atrophied with persistent fetal lobulation. Microscopic examination showed a diffuse global sclerosis. However, despite of the smaller size of glomeruli, the nephron number remained similar to that of the age-matched control. Whole-exome sequencing revealed that the affected child was compound heterozygous for novel truncating LAMB2 mutations: a 4-bp insertion (p.Gly1693Alafs*8) and a splicing donor-site substitution (c.1225 + 1G > A), presumably deleting the coiled-coil domains that form the laminin 5-2-1 heterotrimer complex. CONCLUSIONS: Our case represents a variation of Pierson syndrome that accompanies CNS with unilateral ocular hypoplasia. The average number but smaller glomeruli could reflect either mal-development or glomerulosclerosis. Heterogeneous clinical expression of LAMB2 defects may associate with the difference in fetal ß1 subtype compensation among affected tissues. Further study is necessary to evaluate incidence and features of auditory defect under LAMB2 deficiency.

Monoclonal immunoglobulin-associated proliferative glomerulonephritis characterized by organized deposits of striated ultra-substructures: A case report.

We herein report the case of a 64-year-old male who presented with progressive glomerulonephritis notable for organized and striated ultra-substructures. The patient was diagnosed with hypertension and proteinuria 3 years prior to admission and subsequently developed nephrotic syndrome and impairment of renal function. Laboratory tests did not reveal any evidence of infections or autoimmune diseases. Monoclonal gammopathy was not detected in serum or urine, although a small population of abnormal plasma cell clones was detected by flow cytometry. A renal biopsy showed mesangial and endocapillary proliferative glomerulonephritis with lobular accentuation, accompanied with focal and segmental double-contour formation. Additionally, moderate tubulointerstitial scarring and arteriosclerosis were noted. Immunofluorescence staining revealed positive staining for IgG, IgM, C3, C1q, and fibrinogen. IgG subclass and light chain staining showed restricted positivity for IgG1κ. Electron microscopy demonstrated massive amounts of subendothelial deposits with a fibrillary and branching profile. At higher magnification, a periodic striated pattern was observed within the microfilament-like structures. Immunohistochemical staining was negative for myoglobin, laminin, and collagens (type III and IV). Steroid and antihypertensive therapy did not show improvement in renal function. The second biopsy performed 2 years later revealed a similar lobular proliferative glomerulonephritis pattern with more extensive tubulointerstitial damage, indicating poor response to immunosuppressive therapy. The patient progressed to end-stage renal disease and required hemodialysis. We discuss the possible origins of the deposits with unusual substructures observed in this case.

Determinants of the Change in Arterial Stiffness in Peritoneal Dialysis Patients.

Arterial stiffness is an important risk factor for cardiovascular disease (CVD) in patients with end-stage renal failure. However, little is known about the factors that contribute to arterial rigidity in peritoneal dialysis (PD) patients. The aim of this study was to define the pattern and determinants of the longitudinal change in arterial stiffness after PD initiation.Arterial stiffening was estimated for 46 PD patients by using brachial-ankle pulse wave velocity (baPWV) and carotid intima-media thickness (cIMT). The cross-sectional relationship between the arterial markers and their clinical determinants was studied. The longitudinal effects of blood pressure (BP), body fluid status, and glucose were studied over the two years after initiating PD.Multivariate analysis showed that higher baPWV was associated positively with urinary protein excretion (P < 0.001), systolic BP (P = 0.001), and hemoglobin A1c (P = 0.003). In contrast, increased cIMT correlated with smoking (P = 0.004) and hypoalbuminemia (P = 0.04), suggesting that endothelial dysfunction is implicated in the atherogenic process. Neither cIMT nor baPWV correlated significantly with other PD-related covariates of volume overload, peritoneal solute transport, kidney function, and C-reactive protein. Longitudinal observation demonstrated that BP had a greater influence on baPWV changes than hyperglycemia or fluid status.Our study indicates that 1) baPWV represent an arterial marker that integrates multifactorial interaction between modifiable variables including BP and plasma glucose; and 2) intervention aimed at controlling BP as well as nutritional conditions (glucose and albumin) may reduce CVD risk in PD patients.

Comparison of live donor pre-transplant and recipient post-transplant renal volumes.

BACKGROUND: Live donor pre-transplant and recipient post-transplant kidney volumes based on three-dimensional computed tomography (3DCT) have been related to post-transplant renal function. We examined this association and the effect of sex/size differences between donor and recipient on kidney growth rate. METHODS: We retrospectively reviewed 30 live donors who underwent pre-transplant and post-transplant 3DCT. We determined donor (Dvol) and recipient renal volumes (Rvol) based on 3DCT and calculated changes in graft volume after transplantation (Vol-ratio). We also divided Dvol by recipient body weight (Dvol/RWgt) and compared the correlations between Vol-ratio and Dvol/RWgt and post-transplant renal function after one yr. We determined the rates of change in kidney volume and renal function according to the sexes of the donor and recipient. RESULTS: The mean Dvol and Rvol were 141.7 and 178.4 mL, respectively. The mean Vol-ratio was 127.3%. Dvol/RWgt showed a significant linear correlation with remaining renal function after one yr (r = 0.6745, p < 0.0001). The combination of female donor and male recipient resulted in the fastest increase in kidney volume (p < 0.001) and highest level of proteinuria (p < 0.001). CONCLUSIONS: Pre-transplant and post-transplant kidney volumes are correlated with post-transplant graft function, and graft growth is affected by the relative sexes of the recipient and donor.

Mechanism of cystogenesis by Cd79a-driven, conditional mTOR activation in developing mouse nephrons.

Polycystic kidney disease (PKD) is a common genetic disorder arising from developmental and postnatal processes. Defects in primary cilia and their signaling (eg, mTOR) underlie the pathogenesis. However, how mTOR regulates tubular integrity remains unclear. The paucity of faithful models has limited our understanding of pathogenesis and, therefore, the refinement of therapeutic targets. To understand the role of mTOR in early cystogenesis, we studied an in-house mouse model, Cd79a-Cre;Tsc1ff. (Cd79a-Tsc1 KO hereafter), recapitulating human autosomal-dominant PKD histology. Cre-mediated Tsc1 depletion driven by the promoter for Cd79a, a known B-cell receptor, activated mTORC1 exclusively along the distal nephron from embryonic day 16 onward. Cysts appeared in the distal nephron at 1 weeks of age and mice developed definite PKD by 4 weeks. Cd79a-Tsc1 KO tubule cells proliferated at a rate comparable to controls after birth but continued to divide even after postnatal day 14 when tubulogenesis is normally completed. Apoptosis occurred only after 9 weeks. During postnatal days 7-11, pre-cystic Cd79a-Tsc1 KO tubule cells showed cilia elongation, aberrant cell intercalation, and mitotic division, suggesting that defective cell planar polarity (PCP) may underlie cystogenesis. mTORC1 was activated in a portion of cyst-lining cells and occasionally even when Tsc1 was not depleted, implying a non-autonomous mechanism. Our results indicate that mTORC1 overactivation in developing distal tubules impairs their postnatal narrowing by disrupting morphogenesis, which orients an actively proliferating cell toward the elongating axis. The interplay between mTOR and cilium signaling, which coordinate cell proliferation with PCP, may be essential for cystogenesis.

Characterization of cytoskeletal and structural effects of INF2 variants causing glomerulopathy and neuropathy.

Focal segmental glomerulosclerosis (FSGS) is a common glomerular injury leading to end-stage renal disease. Monogenic FSGS is primarily ascribed to decreased podocyte integrity. Variants between residues 184 and 245 of INF2, an actin assembly factor, produce the monogenic FSGS phenotype. Meanwhile, variants between residues 57 and 184 cause a dual-faceted disease involving peripheral neurons and podocytes (Charcot-Marie-Tooth CMT/FSGS). To understand the molecular basis for INF2 disorders, we compared structural and cytoskeletal effects of INF2 variants classified into two subgroups: One (G73D, V108D) causes the CMT/FSGS phenotype, and the other (T161N, N202S) produces monogenic FSGS. Molecular dynamics analysis revealed that all INF2 variants show distinct flexibility compared to the wild-type INF2 and could affect stability of an intramolecular interaction between their N- and C-terminal segments. Immunocytochemistry of cells expressing INF2 variants showed fewer actin stress fibers, and disorganization of cytoplasmic microtubule arrays. Notably, CMT/FSGS variants caused more prominent changes in mitochondrial distribution and fragmentation than FSGS variants and these changes correlated with the severity of cytoskeletal disruption. Our results indicate that CMT/FSGS variants are associated with more severe global cellular defects caused by disrupted cytoskeleton-organelle interactions than are FSGS variants. Further study is needed to clarify tissue-specific pathways and/or cellular functions implicated in FSGS and CMT phenotypes.