Ab in Lens in Down Syndrome Figure 1. Phenotypic expression of representative supranuclear cataracts in Down syndrome. (A-C) Representative supranuclear cataract in a 46-year-old male with Down syndrome observed by slit lamp biomicroscopy. (A) Broad-beam illumination demonstrates numerous cerulean coronary ‘‘blue dot’’ lens opacities. Asterisk denotes first Purkinje image (corneal specular reflection). (B) Retro-illumination reveals a distinctive peripheral ring of opacification in the subequatorial supranuclear subregion of the lens. Red reflex is imparted by retinal reflection. Corneal Purkinje image is evident centrally (asterisk). (C) Inverted grayscale rendering of the retro-illumination image highlights the circumferential subequatorial supranuclear opacification (dashed circle) that characterizes the distinctive Down syndrome cataract phenotype. Corneal Purkinje image is evident centrally (asterisk). (D) Static light scattering intensity plotted as a function of anatomical position within the lens. Axial location is referenced to the dashed line and anatomical orientation axes represented in the inset. (E-H) Representative stereophotomicroscopic images of ex vivo lenses from subjects with Down syndrome of indicated ages and gender. Colored dots indicate superior and inferior extent of the slit beam ribbon defining the posterior surface of each imaged lens. White dots indicate superior and inferior extent of the light reflex on the anterior aspect of each imaged lens. (E) Lens from a 2-year-old male with Down syndrome. Slit beam photomicroscopy demonstrates a grossly normal transparent lens. (F) Lens from a 42-year-old female with Down syndrome. Supranuclear opacification is evident in a semicircular arc (dashes) with prominent cortical spokes and moderate lenticular brunescence. (G) Lens from a 61-year-old female with Down syndrome. Distinctive supranuclear opacification describes an incomplete supranuclear arc (dashes). Cortical spokes and moderate lenticular brunescence are present. (H) Lens from a 64-year-old male with Down syndrome. Prominent circumferential opacification is present as a subequatorial supranuclear ring cataract (dashed circle). This cataract describes an annular half torroid that follows the anteroposterior orientation of the supranuclear fiber cells enveloping the peripheral extent of the embryonic nucleus. Cortical spokes and moderate lenticular brunescence are evident. This same lens is presented as a stereo image pair with and without intact zonule fibers (Fig. S1 and Fig. 2, respectively). See text for details. doi:10.1371/journal.pone.0010659.g001 demonstrated apparent age-dependent supranuclear lens pathol- ogy (Fig. 1E-H) that was phenotypically indistinguishable from that previously reported in late-onset sporadic AD (Fig. 1F-H) [28]. A representative stereo image of a lens from a 64-year-old male with DS (Fig. 2A) illustrates an advanced circumferential supranuclear cataract characteristic of the DS phenotype. The phenotypic features of this distinctive cataract phenotype are demonstrated in the same lens observed by slit lamp photomi- croscopy (Fig. 1H) and as a stereo image pair with intact zonule fibers (Fig. S1). The cataract phenotype observed in DS was strikingly similar to the mature subequatorial supranuclear cataracts previously reported in advanced AD (Fig. 2B; [28]). This distinctive DS-associated cataract was not present in age- matched normal control subjects nor was this focal lens pathology associated with global swelling, diffuse opacification, or capsular disruption indicative of postmortem tissue injury. Histochemical and Ultrastructural Analyses The phenotypic correspondence of the distinctive cataracts in DS and AD encouraged us to investigate the possibility of Ab pathology in DS lenses. Orientation to the anatomy of the adult human lens is shown (Fig. 3A,B) and compared to an historical drawing (Fig. 3C) illustrating the distinctive localized supranuclear lens pathology in a 37-year-old subject with clinical features consistent with Down syndrome [23]. Amyloid histochemical analysis of DS lenses in the present study demonstrated Congo red staining (Fig. 3D) and intense apple-green birefringence (Fig. 3E) under cross-polarized illumination, findings consistent with the tinctorial requirements for designation as amyloid pathology [30,31]. Amyloid histopathology was not evident in a lens from an age- and sex-matched normal control donor (Fig. 3F) and co- localized with lens pathology and Ab immunoreactivity as demonstrated by specific Ab immunoreactivity in the deep cortical, supranuclear, and anterior epithelial subregions (Fig. 3G). Anti-Ab immunoreactivity was not detected in adjacent control sections probed with immunodepleted detection antibody (Fig. 3H) or in lens specimens from age- and sex-matched normal control donors (Fig. 3I). Anti-Ab immunogold electron microscopy revealed immunoreactive aggregates (,5–50 nm) that localized to the cytoplasm of supranuclear fiber cells in DS lenses (Fig. 3J,K) but was not observed in adjacent control sections probed with PLoS ONE | www.plosone.org 4 May 2010 | Volume 5 | Issue 5 | e10659