Kristel Klaassen Ljubičić

Assistant Research Professor
Laboratory for Molecular Biomedicine

Institute of Molecular Genetics and Genetic Engineering (IMGGE),
University of Belgrade 

Vojvode Stepe 444a, 11042 Belgrade 152, Serbia
Mobile: +381 65 3976 445
Phone:  +381 11 397 64 45
Fax:     +381 11 397 58 08


2015 - PhD in Molecular Biology, Faculty of Biology (FB), University of Belgrade (UB)
(Thesis: Impact of variants in coding and noncoding regions of disease-causing and modifier genes on phenotype of patients with hyperphenylalaninemia)
2010 - Diploma (equivalent to M.Sc.) in Molecular biology and physiology, FB, UB 


2016 - Research Associate at Laboratory for Molecular Biomedicine, IMGGE
2012 - 2016 - Research Assistant at Laboratory for Molecular Biomedicine, IMGGE
2011 - 2012 - Research Trainee at Laboratory for Molecular Hematology (today Laboratory for Molecular Biomedicine), IMGGE
2011 - Visiting researcher at Centro di Ricerca M. Tettamanti, Universita di Milano-Biccoca, Monza, Italy
2012 - 2014 - Visiting researcher at Centro de Biologia Molecular “Severo Ochoa”, Universidad Autonoma, Madrid, Spain 


2011 to present - Researcher at Laboratory for Molecular Biomedicine, IMGGE, UB 


My research is focused on the molecular basis of hyperphenylalaninemia (HPA), the most common inborn error of amino acid metabolism. HPA is caused either by a deficiency of the enzyme phenylalanine hydroxylase (PAH) or its cofactor, tetrahydrobiopterin (BH4). The aim of the research is to optimize the molecular-genetic diagnostics, characterize new mutations and analyze the mutation effect, in order to predict the patients’ phenotype based on the genotype. Nevertheless, as additional genetic factors contributing to HPA phenotype remain unknown, the aim is to identify new phenotype modulators. These modulators, such as new transcription regulators in the PAH gene, as well as putative modifier genes, could lead toward a more refined prediction of the disease outcome and personalized therapy. 


Klaassen K, Stankovic B, Kotur N, Djordjevic M, Zukic B, Nikcevic G, Ugrin M, Spasovski V, Srzentic S, Pavlovic S, Stojiljkovic M. New PAH gene promoter KLF1 and 3'-region C/EBPalpha motifs influence transcription in vitro. J Appl Genet. 2016 Jul 22. [Epub ahead of print]

Stojiljkovic M, Klaassen K, Djordjevic M, Sarajlija A, Brasil S, Kecman B, Grkovic S, Kostic J, Rodriguez-Pombo P, Desviat LR, Pavlovic S, Perez B. Molecular and phenotypic characteristics of seven novel mutations causing branched-chain organic acidurias. Clin Genet 2016 Feb 2. [Epub ahead of print]

Ugrin M, Stojiljkovic M, Zukic B, Klaassen K, Katsila T, Vasiljevic J, Dokmanovic L, Janic D, Patrinos GP, Pavlovic S. Functional Analysis of an (A)γ-Globin Gene Promoter Variant (HBG1: g.-225_-222delAGCA) Underlines Its Role in Increasing Fetal Hemoglobin Levels Under Erythropoietic Stress. Hemoglobin 2016; 40(1):48-52.

Milacic I, Barac M, Milenkovic T, Ugrin M, Klaassen K, Skakic A, Jesic M, Joksic I, Mitrovic K, Todorovic S, Vujovic S, Pavlovic S, Stojiljkovic M. Molecular genetic study of congenital adrenal hyperplasia in Serbia: novel p.Leu129Pro and p.Ser165Pro CYP21A2 gene mutations. J Endocrinol Invest 2015; 38(11): 1199-210.

Jančić I, Šefik-Bukilica M, Živojinović S, Damjanov N, Spasovski V, Kotur N, Klaassen K, Pavlović S, Bufan B, and Arsenović-Ranin N. Influence of Promoter Polymorphisms of the TNF-α (-308G/A) And IL-6 (-174G/C) Genes On Therapeutic Response To Etanercept In Rheumatoid Arthritis. J Med Biochem 2015; 34(4): 414–421.

Stojiljkovic M, Klaassen K, Djordjevic M, Sarajlija A, Kecman B, Ugrin M, Zukic B, Desviat LR, Pavlovic S, Perez B. Tetrahydrobiopterin deficiency among Serbian patients presenting with hyperphenylalaninemia. J Pediatr Endocrinol Metab 2015; 28(3-4): 477-80.

Stojiljkovic Petrovic M, Klaassen K, Pavlovic S. Molecular characteristics, phenotypic diversity and genotype-estimated therapeutic responsiveness of Serbian patients with phenylketonuria. J Med Biochem 2014; 33: 1–11.

Klaassen K, Djordjevic M, Stojiljkovic Petrovic M, Pavlovic S. Association of mitochondrial DNA variants and cognitive impairment of PKU patients. J Med Biochem 2013; 32: 337–343.

Djordjevic M, Klaassen K, Sarajlija A, Tosic N, Zukic B, Kecman B, Ugrin M, Spasovski V, Pavlovic S, Stojiljkovic M. Molecular Genetics and Genotype-Based Estimation of BH4-Responsiveness in Serbian PKU Patients: Spotlight on Phenotypic Implications of p.L48S. JIMD Rep 2013; 9: 49-58.

Kotur N, Stankovic B, Kassela K, Georgitsi M, Vicha A, Leontari I, Dokmanovic L, Janic D, Krstovski N, Klaassen K, Radmilovic M, Stojiljkovic M, Nikcevic G, Simeonidis A, Sivolapenko G, Pavlovic S, Patrinos GP, Zukic B. 6-mercaptopurine influences TPMT gene transcription in a TPMT gene promoter variable number of tandem repeats-dependent manner. Pharmacogenomics 2012; 13(3): 283-95.

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