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Brunella Franco

Principal Investigator
Core Facilities Coordinator

Professor of Medical GeneticsDepartment of Translational Medicine, University of Naples "Federico II", Italy

Cilia and Human Diseases: Insights from the OFD Type I Syndrome

 Cilia are microtubule-based organelles protruding from the cell surface of almost all mammalian cells and exert diverse motility and sensory function within the cell. Work from different groups has revealed that cilia have crucial roles in cell signalling pathways and in maintaining cellular homeostasis. The link between pathological phenotypes and ciliary dysfunction in humans was proposed in the 1970s. However, only recently mutations in proteins that localize to the basal body and axoneme of primary cilia were causally related to human diseases. Collectively, these human syndromes are called “ciliopathies”, disorders defined by unique clinical criteria, but which present many overlapping phenotypes such as retinal degeneration, polydactyly, situs inversus, mental retardation and CNS malformations, encephalocele and cysts in the kidney, liver and pancreas. Thousands of proteins potentially involved in ciliary function have been identified. However, much remains to be determined on the biology and functions of this complex organelle of growing biomedical importance.

Our laboratory has been involved for the past few years in the study of the pathogenetic mechanisms underlying the Oral-facial-digital type I syndrome (OFD1), which we demonstrated to be ascribed to dysfunction of primary cilia. To gain further insight on the molecular mechanisms and pathogenesis of ciliopathies, our laboratory presently focuses on multidisciplinary approaches, which include:

  • Systems biology approaches to perform a global analysis of ciliary gene expression. This analysis will allow the identification of specific gene regulatory networks underlying cilia functions
  • Cell biology approaches to study the role of the cytoskeleton in basal body function and ciliogenesis in in vitro and in vivo models
  • Functional studies to unravel the link between ciliary proteins and ubiquitin-dependent proteasomal degradation


The Molecular Basis of Microphthalmia with Linear Skin Lesions (MLS) Syndrome

The Microphthalmia with linear skin defects (MLS) syndrome is a rare X-linked dominant male-lethal neuro-developmental disorder associated to mutations in the holocytochrome c-type synthetase (HCCS) transcript. Female patients display unilateral or bilateral microphthalmia and linear skin defects, additional features include central nervous system (CNS) malformation and mental retardation. HCCS codifies a mitochondrial protein that catalyzes the attachment of heme to both apocytochrome c and c1, necessary for proper functioning of the mitochondrial respiratory chain. Although mutation analysis clearly indicates a role for HCCS in the pathogenesis of this genetic condition, the molecular mechanisms underlying the developmental anomalies in the presence of HCCS dysfunction are still unknown. Previous studies demonstrated the early lethality of mouse embryonic Hccs knock-out stem cells. To overcome the problem of the possible embryonic lethality, we generated an animal model for MLS syndrome in the Medaka fish (Oryzia latipes) using a morpholino-based technology. Three specific morpholinos directed against different portions of the olhccs transcript have been designed and injected and our data indicate that all morpholinos effectively downregulate the expression of the olhccs gene. The injection of the three different morpholinos resulted in a pathological phenotype, which resembles the human condition. This animal model recapitulates the phenotype observed in MLS syndrome. Our laboratory is currently involved in the characterization of this model aiming at:

  • Studying the role of HCCS in eye development and in mitochondrial functions and programmed cell death
  • Defining the pathogenetic mechanisms underlying microphtalmia with linear skin lesions (MLS) syndrome
Liu YP*, Tsai IC*, Morleo* M, Oh EC, Leitch CC, Massa F, Lee BH, Parker DS, Finley D, Zaghloul NA, Franco B+, Katsanis N+ (2014). Ciliopathy proteins regulate paracrine signaling by modulating proteasomal degradation of mediators. J Clin Invest. 124(5):2059-7. doi:10.1172/JCI71898. *Equally contributing. +Corresponding authors

Amato R, Morleo M, Giaquinto L, di Bernardo D, Franco B (2014). A network-based approach to dissect the cilia/centrosome complex interactome. BMC Genomics. 7;15:658. doi:10.1186/1471-2164-15-658. 

Indrieri A, Conte I, Chesi G, Romano A, Quartararo J, Tatè R, Ghezzi D, Zeviani M, Goffrini P, Ferrero I, Bovolenta P, Franco B (2013). The impairment of HCCS leads to MLS syndrome by activating a non-canonical cell death pathway in the brain and eyes. EMBO Mol Med. 5(2): 280-93. doi:10.1002/emmm.201201739. 

Indrieri A, van Rahden VA, Tiranti V, Morleo M, Iaconis D, Tammaro R, D'Amato I, Conte I, Maystadt I, Demuth S, Zvulunov A, Kutsche K, Zeviani M, Franco B (2012).Mutations in COX7B cause microphthalmia with linear skin lesions, an unconventional mitochondrial disease. Am J Hum Genet. 91(5): 942-9. doi:10.1016/j.ajhg.2012.09.016.

Ferrante MI, Zullo A, Barra A, Bimonte S, Messaddeq N, Studer M, Dolle P, Franco B (2006). Oral-facial-digital type I protein is required for primary cilia formation and left-right axis specification. Nat Genet. 38:112-117. doi:10.1038/ng1684.

Brunella Franco MD

Cell Biology and Disease Mechanisms

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