Figure 1.
Clinical characteristics of patients with identified RPA1 variants. (A) Germline RPA1 variants identified in 4 pedigrees using exome sequencing. Black filled, open dotted, and open symbols denote affected individuals with heterozygous (het) RPA1 mutations, unaffected carriers, and unaffected family members without mutations, respectively. (B) Top panel: schematic of the RPA1 gene with 17 coding exons illustrated as black lines and untranslated regions shown in red (NM_002945.5). The 3 unique patient variants are located on exons 8, 9, and 10. Bottom panel: Human RPA1 protein illustration with 4 oligonucleotide/oligosaccharide–binding fold domains F, A, B, and C with amino acid boundaries shown below. Oligonucleotide/oligosaccharide–binding folds A, B, and C are ssDNA-binding domains. Red arrows indicate location of 3 RPA1 missense alterations. (C) BM findings in patient cohort (top panel): P1 BM aspirate smears (Wright-Giemsa staining) at time of clinical presentation at age 10 years showing marked reduction in cell content with hypoplasia of all lineages (left image) and megaloblastic maturation of erythroid precursors (middle image). P2 BM infiltrated with myeloblasts (right image) consistent with MDS with excess blasts. Pulmonary findings by chest computed tomography (CT) imaging in patient cohort (middle panel): P2 chest CT scan (left image) during hospitalization showing necrotizing pneumonitis with diffuse ground-glass opacities and large air-filled cavities with differential diagnosis, including pulmonary GVHD, opportunistic infection(s), pulmonary fibrosis, or a combination of the aforementioned conditions. P3 presented at age 58 years with cough and exertional dyspnea with chest CT scan (middle image) findings showing intralobular reticulations with traction bronchiectasis and mild honeycombing, with left asymmetric and basal, subpleural predominance. At 61 years, P3 chest CT scan (right image) showed significant progression of asymmetric lung fibrosis with left predominance and massive basal honeycombing. Mucocutaneous abnormalities in P1 (bottom panel): oral leukoplakia at 19 years of age (top left image) with mild improvement at 25 years of age (top right image), nail dystrophy (bottom left image), and reticular skin pigmentation on the ventral neck (bottom right image). (D) Telomere length analysis by flow cytometry–based FISH was conducted in lymphocytes of P1 (red circles) and P4 (blue circles). P1 telomere length is less than the first percentile at 24 and 27 years of age (red circles). P4 telomere length is at the fifth percentile at 1.75 years of age and less than the first percentile at age 3.33 years (blue circles). All measurements were performed in triplicate, and mean telomere length was calculated in kilobases in relation to the internal control (bovine thymocytes) with known telomere length. A total of 356 healthy controls used for calculation of the first (solid line, bottom), fifth (dashed line, bottom), 95th (dashed line, top), and 99th (solid line, top) percentile curves. (E) TRF analysis in peripheral blood DNA from P2 and family and P3 compared with healthy age–matched control (Ctrl), digested with HinfI and RsaI enzymes followed by separation on 0.7% agarose gel.

Clinical characteristics of patients with identified RPA1 variants. (A) Germline RPA1 variants identified in 4 pedigrees using exome sequencing. Black filled, open dotted, and open symbols denote affected individuals with heterozygous (het) RPA1 mutations, unaffected carriers, and unaffected family members without mutations, respectively. (B) Top panel: schematic of the RPA1 gene with 17 coding exons illustrated as black lines and untranslated regions shown in red (NM_002945.5). The 3 unique patient variants are located on exons 8, 9, and 10. Bottom panel: Human RPA1 protein illustration with 4 oligonucleotide/oligosaccharide–binding fold domains F, A, B, and C with amino acid boundaries shown below. Oligonucleotide/oligosaccharide–binding folds A, B, and C are ssDNA-binding domains. Red arrows indicate location of 3 RPA1 missense alterations. (C) BM findings in patient cohort (top panel): P1 BM aspirate smears (Wright-Giemsa staining) at time of clinical presentation at age 10 years showing marked reduction in cell content with hypoplasia of all lineages (left image) and megaloblastic maturation of erythroid precursors (middle image). P2 BM infiltrated with myeloblasts (right image) consistent with MDS with excess blasts. Pulmonary findings by chest computed tomography (CT) imaging in patient cohort (middle panel): P2 chest CT scan (left image) during hospitalization showing necrotizing pneumonitis with diffuse ground-glass opacities and large air-filled cavities with differential diagnosis, including pulmonary GVHD, opportunistic infection(s), pulmonary fibrosis, or a combination of the aforementioned conditions. P3 presented at age 58 years with cough and exertional dyspnea with chest CT scan (middle image) findings showing intralobular reticulations with traction bronchiectasis and mild honeycombing, with left asymmetric and basal, subpleural predominance. At 61 years, P3 chest CT scan (right image) showed significant progression of asymmetric lung fibrosis with left predominance and massive basal honeycombing. Mucocutaneous abnormalities in P1 (bottom panel): oral leukoplakia at 19 years of age (top left image) with mild improvement at 25 years of age (top right image), nail dystrophy (bottom left image), and reticular skin pigmentation on the ventral neck (bottom right image). (D) Telomere length analysis by flow cytometry–based FISH was conducted in lymphocytes of P1 (red circles) and P4 (blue circles). P1 telomere length is less than the first percentile at 24 and 27 years of age (red circles). P4 telomere length is at the fifth percentile at 1.75 years of age and less than the first percentile at age 3.33 years (blue circles). All measurements were performed in triplicate, and mean telomere length was calculated in kilobases in relation to the internal control (bovine thymocytes) with known telomere length. A total of 356 healthy controls used for calculation of the first (solid line, bottom), fifth (dashed line, bottom), 95th (dashed line, top), and 99th (solid line, top) percentile curves. (E) TRF analysis in peripheral blood DNA from P2 and family and P3 compared with healthy age–matched control (Ctrl), digested with HinfI and RsaI enzymes followed by separation on 0.7% agarose gel.

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