Biomedical subjects

Giovanna Alfano

Publications and source records attributed to Giovanna Alfano.

4 recordsLinked to original sources

PubMed2005

Natural antisense transcripts associated with genes involved in eye development.

Natural antisense transcripts (NATs) are a class of genes whose role in controlling gene expression is becoming more and more relevant. We describe the identification of eight novel mouse NATs associated with transcription factors (Pax6, Pax2, Six3, Six6, Otx2, Crx, Rax and Vax2) that play an important role in eye development and function. These newly identified NATs overlap with the mature processed mRNAs or with the primary unprocessed transcript of their corresponding sense genes, are predicted to represent either protein coding or non-coding RNAs and undergo extensive alternative splicing. Expression studies, by both RT-PCR and RNA in situ hybridization, demonstrate that most of these NATs, similarly to their sense counterparts, display a specific or predominant expression in the retina, particularly at postnatal stages. We found a significant reduction of the expression levels of one of these NATs, Vax2OS (Vax2 opposite strand) in a mouse mutant carrying the inactivation of Vax2, the corresponding sense gene. In addition, we overexpressed another NAT, CrxOS, in mouse adult retina using adeno-associated viral vectors and we observed a significant decrease in the expression levels of the corresponding sense gene, Crx. These results suggest that these transcripts are functionally related to their sense counterparts and may play an important role in regulating the molecular mechanisms that underlie eye development and function in both physiological and pathological conditions.

Alternative Splicing↗

PubMed2003

Identification and characterisation of the retinitis pigmentosa 1-like1 gene (RP1L1): a novel candidate for retinal degenerations.

Retinitis pigmentosa (RP) is the most common form of inherited retinopathy, with an approximate incidence of 1 in 3700 individuals worldwide. Mutations in the retinitis pigmentosa 1 (RP1) gene are responsible for about 5-10% cases of autosomal dominant RP. The RP1 gene is specifically expressed in the photoreceptor layers of the postnatal retina and encodes a predicted protein characterised by the presence of two doublecortin (DC) domains, known to be implicated in microtubule binding. We identified and characterised, both in human and in mouse, a novel mammalian gene, termed Retinitis Pigmentosa1-like1 (RP1L1), because of its significant sequence similarity to the RP1 gene product. The sequence homology between RP1 and RP1L1 was found to be mostly restricted to the DC domains and to the N-terminal region, including the first 350 amino acids. The RP1L1 gene was also found to be conserved in distant vertebrates, since we identified a homologue in Fugu rubripes (pufferfish). Similar to RP1, RP1L1 expression is restricted to the postnatal retina, as determined by semiquantitative reverse transcriptase-PCR and Northern analysis. The retina-specific expression and the sequence similarity to RP1 render RP1L1 a potential candidate for inherited retinal disorders.

Amino Acid Motifs↗

PubMed2002

Characterization of MPP4, a gene highly expressed in photoreceptor cells, and mutation analysis in retinitis pigmentosa.

Membrane-associated guanylate kinase (MAGUK) proteins are cell-cell contact organizing molecules that mediate targeting, clustering and anchoring of proteins at synapses and other cell junctions. MAGUK proteins may contain multiple protein-protein interaction motifs including PDZ, SH3 and guanylate kinase (GuK) domains. In this study, we performed a detailed analysis of the expression pattern of MPP4, a recently described member of the MAGUK protein family. We confirmed that this gene is highly expressed in retina, and demonstrate that it is also present, at lower levels, in brain. We identified a new retina specific isoform encoding a predicted protein lacking 71 amino acids. This protein region contains a newly identified L27 domain, another module playing a role in protein-protein interaction. By RNA in situ hybridization, Mpp4 expression was found to be localized to photoreceptor cells in postnatal retina. The MPP4 gene is localized to chromosome 2, in band 2q31-33, where a locus for autosomal recessive retinitis pigmentosa (RP26) has been mapped. Mutation analysis of the entire open reading frame of the MPP4 gene in a RP26 family revealed no pathologic mutations. In addition, we did not identify mutations in a panel of 300 unrelated patients with retinitis pigmentosa.

Alternative Splicing↗

PubMed2002

Vax2 inactivation in mouse determines alteration of the eye dorsal-ventral axis, misrouting of the optic fibres and eye coloboma.

Vax2 is a homeobox gene whose expression is confined to the ventral region of the prospective neural retina. Overexpression of this gene at early stages of development in Xenopus and in chicken embryos determines a ventralisation of the retina, thus suggesting its role in the molecular pathway that underlies eye development. We describe the generation and characterisation of a mouse with a targeted null mutation of the Vax2 gene. Vax2 homozygous mutant mice display incomplete closure of the optic fissure that leads to eye coloboma. This phenotype is not fully penetrant, suggesting that additional factors contribute to its generation. Vax2 inactivation determines dorsalisation of the expression of mid-late (Ephb2 and Efnb2) but not early (Pax2 and Tbx5) markers of dorsal-ventral polarity in the developing retina. Finally, Vax2 mutant mice exhibit abnormal projections of ventral retinal ganglion cells. In particular, we observed the almost complete absence of ipsilaterally projecting retinal ganglion cells axons in the optic chiasm and alteration of the retinocollicular projections. All these findings indicate that Vax2 is required for the proper closure of the optic fissure, for the establishment of a physiological asymmetry on the dorsal-ventral axis of the eye and for the formation of appropriate retinocollicular connections.

Animals↗