You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Variant", "Disease", "Species", "CellLine", "Chemical", "Gene"].

Please return the output as a JSON object of the format: {"CellLine": ["hRPTEC", ...], "Chemical": ["Glucose", ...], "Disease": ["Diabetes", ...], "Gene": ["HNF-6", ...], "Species": ["Patients", ...], "Variant": ["Pro75Ala", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Association of a FGFR-4 gene polymorphism with bronchopulmonary dysplasia and neonatal respiratory distress. BACKGROUND: Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease of premature birth, characterized by impaired alveolar development and inflammation. Pathomechanisms contributing to BPD are poorly understood. However, it is assumed that genetic factors predispose to BPD and other pulmonary diseases of preterm neonates, such as neonatal respiratory distress syndrome (RDS). For association studies, genes upregulated during alveolarization are major candidates for genetic analysis, for example, matrix metalloproteinases (MMPs) and fibroblast growth factors (FGFs) and their receptors (FGFR). OBJECTIVE: Determining genetic risk variants in a Caucasian population of premature neonates with BPD and RDS. Methods. We genotyped 27 polymorphisms within 14 candidate genes via restriction fragment length polymorphism (RFLP): MMP-1, -2, -9, and -12, -16, FGF receptors 2 and 4, FGF-2, -3, -4, -7, and -18, Signal-Regulatory Protein a (SIRPA) and Thyroid Transcription Factor-1 (TTF-1). RESULTS: Five single nucleotide polymorphisms (SNPs) in MMP-9, MMP-12, FGFR-4, FGF-3, and FGF-7 are associated (P < 0.05) with RDS, defined as surfactant application within the first 24 hours after birth. One of them, in FGFR-4 (rs1966265), is associated with both RDS (P = 0.003) and BPD (P = 0.023). CONCLUSION: rs1966265 in FGF receptor 4 is a possible genetic key variant in alveolar diseases of preterm newborns.
{"CellLine": [], "Chemical": [], "Disease": ["bronchopulmonary dysplasia", "pulmonary diseases", "inflammation", "neonatal respiratory distress syndrome", "impaired alveolar development", "RDS", "alveolar diseases", "neonatal respiratory distress", "lung disease", "premature birth", "BPD", "Bronchopulmonary dysplasia"], "Gene": ["FGFR-4", "matrix metalloproteinases", "fibroblast growth factors", "FGF-3", "MMP-12", "FGF receptors 2 and 4", "FGF-7", "FGFs", "Thyroid Transcription Factor-1", "FGF receptor 4", "MMPs", "FGF-2, -3, -4, -7, and -18", "Signal-Regulatory Protein a", "SIRPA", "MMP-1, -2, -9, and -12, -16", "MMP-9", "TTF-1", "FGFR"], "Species": [], "Variant": ["rs1966265"]}