Biomedical subjects

Tadashi Kaname

Publications and source records attributed to Tadashi Kaname.

3 recordsLinked to original sources

PubMed2026

Postzygotic biallelic inactivation of FDFT1 underlies solitary lesion formation in porokeratosis of Mibelli.

BACKGROUND: Porokeratosis reflects clonal expansion of keratinocytes with biallelic inactivation of mevalonate-cholesterol biosynthesis pathway genes. In disseminated porokeratosis (DP), lesions arise through independent somatic second hits in carriers of heterozygous germline pathogenic variants, whereas porokeratosis of Mibelli (PM) is usually solitary, and its molecular basis remains incompletely defined. OBJECTIVE: To elucidate the molecular basis of solitary PM. METHODS: We analyzed blood and lesional epidermis from seven patients with solitary PM within a 156-patient porokeratosis cohort using deep sequencing, copy-number/SNP profiling, and methylation analysis. RESULTS: Solitary PM plaques were larger and more irregular than the annular DP lesions. No pathogenic germline variants were detected in MVK, PMVK, MVD, FDPS, or FDFT1. Three patients had somatic biallelic genetic inactivation of FDFT1 through putative deleterious variants and/or focal microdeletions. The remaining four showed FDFT1 promoter hypermethylation with loss of heterozygosity (LOH) at the FDFT1 locus due to copy-neutral LOH or a monoallelic 8p deletion, consistent with early monoallelic epigenetic silencing, followed by genetic loss of the remaining active allele. In one patient, part of the plaque expanded centrifugally over 7.5 years. CONCLUSION: Solitary PM can be driven by postzygotic, lesion-restricted, biallelic inactivation of FDFT1 through genetic or epigenetic mechanisms within a single epidermal clone, promoting clonal expansion. This model may explain the tendency toward solitary PM lesions. The low probability of acquiring postzygotic biallelic inactivation without germline predisposition may underlie solitary PM and suggest a low recurrence risk for offspring, unlike DP driven by germline heterozygosity.

General dermatology↗

PubMed2026

Hearing loss associated with CDC42 in mice and humans (Takenouchi-Kosaki syndrome): CDC42 and RHOQ synergistically function in cochlear hair cells.

CDC42 is involved in multiple signaling pathways, including actin organization and polarity. We previously reported progressive sensorineural hearing loss (SNHL) in inner ear hair cell (HC)-specific Cdc42-knockout (Atoh1-Cre+/-;Cdc42flox/flox) mice. However, the phenotype was milder than expected, suggesting possible redundancy with other Rho-family GTPases. Thereafter, Takenouchi-Kosaki syndrome (TKS), caused by de novo CDC42 mutations and manifesting as SNHL, was reported, in which the p.Y64C mutation was speculated to be constitutively active. However, the relationship between CDC42 status and hearing phenotypes in TKS remains unclear. Using cell models, mouse models, and patient data, we propose that impaired and/or dysregulated cycling between GDP/inactive and GTP/active forms, through either loss-of-function or constitutive activation, can lead to SNHL. Furthermore, to test redundancy, we generated HC-specific Cdc42;RhoQ double-knockout (Atoh1-Cre+/-;Cdc42flox/flox;RhoQflox/flox) mice, which revealed synergistic roles of CDC42 and RHOQ in cochlear HCs. Supporting this synergy, MDCK cells with CDC42 and RHOQ double knockdown showed greater phospho-cofilin, a key regulator of actin turnover, elevation than single knockdowns.

CDC42↗

PubMed2026

Pierson syndrome with numerous dilated tubules masquerading as autosomal recessive polycystic kidney disease: a case report.

Pierson syndrome, characterized by congenital nephrotic syndrome, ocular abnormalities, and neurological defects, is caused by biallelic pathogenic variants in LAMB2. LAMB2 encodes laminin β2, a key component of basement membranes that is predominantly expressed in the glomeruli, eyes, and neuromuscular junctions. The renal histopathology of Pierson syndrome typically shows diffuse mesangial sclerosis (DMS), with occasional tubulointerstitial atrophy and fibrosis. We report a case of Pierson syndrome characterized by DMS and prominent tubular dilatation. A fetal ultrasound at 23 weeks of gestation revealed hyperechoic kidneys, which gradually enlarged, accompanied by the onset of anhydramnios from 31 weeks. The patient was delivered at 39 weeks of gestation, weighing 3,132 g, without placentomegaly. Postnatal respiratory failure due to pulmonary hypoplasia required extracorporeal membrane oxygenation, and hemodialysis was initiated for anuria. Left nephrectomy was performed on day 8 of life, revealing replacement of the renal parenchyma by numerous irregularly dilated tubules with eosinophilic casts. The right kidney reached maximal enlargement by 1 month of age and subsequently began to shrink. Ocular findings included bilateral microcoria and cataracts. Whole-exome sequencing identified compound heterozygous truncating variants in LAMB2 (p.Gln1507Ter and p.Gln1622Ter). This case highlights the need to consider Pierson syndrome in the differential diagnosis of prenatally detected hyperechoic and enlarged kidneys, in addition to polycystic kidney disease.

Female↗