Fig. 1

a Renal histology of kidney donor (I2) and recipient (II1). First: I2 father (kidney donor): COL4A5 immunohistochemistry, moderate deficiency in capillary walls demonstrated by mosaic pattern staining (APAAP). Second: I2 father (kidney donor): electron microscopy, × 20,000, glomerular capillaries with incomplete thinning of the glomerular basement membrane (370.6 nm and 260.8 nm). Third: II1 index patient (kidney recipient): COL4A5 immunohistochemistry, marked deficiency of staining (APAAP). Fourth: II1 index patient (kidney recipient): electron microscopy, × 20,000, capillary with thickening and lamellation of glomerular basement membrane. b Audiograms of all family members showing bilateral sensorineural hearing impairment for high frequencies (4–8 kHz) in the index patient (II1) and both parents (I1 and I2) in contrast to normal hearing in the index patient’s brother (II2). c Family pedigree with index patient (II1) denoted by black arrow. wt, wildtype. d Chromatograms of both heterozygous COL4A3 variants identified in the family: c.1909G > A, p.Gly637Arg and c.4421 T > C, p.Leu1474Pro (NM_000091.4). e COL4A3 protein structure with collagenous triple helix domain, adjacent to N-terminal 7S- and C-terminal non-collagenous (NC) 1 domain. Of note, amino acid substitutions Gly637Arg and Leu1474Pro localize to collagenous and NC1 domain as denoted by arrows