Gene expression often cycles between active and inactive states in eukaryotes, yielding variable or noisy gene expression in the short-term, while slow epigenetic changes may lead to silencing or variegated expression. Understanding how cells control these effects will be of paramount importance to construct biological systems with predictable behaviours. Here we find that a human matrix attachment region (MAR) genetic element controls the stability and heritability of gene expression in cell populations. Mathematical modeling indicated that the MAR controls the probability of long-term transitions between active and inactive expression, thus reducing silencing effects and increasing the reactivation of silent genes. Single-cell short-terms assays revealed persistent expression and reduced expression noise in MAR-driven genes, while stochastic burst of expression occurred without this genetic element. The MAR thus confers a more deterministic behavior to an otherwise stochastic process, providing a means towards more reliable expression of engineered genetic systems.

Prothymosin alpha (ProTalpha) is an acidic nuclear protein the expression of which is related to the proliferation and differentiation processes in mammalian cells. In the present study we have stably transfected HL-60 cells, a biological system that allows the study of both proliferation and differentiation, with recombinant vectors encoding sense and antisense ProTalpha mRNA. In the HL-60 cell clones overexpressing ProTalpha we observed an acceleration in the growth rate, whereas expression of the antisense orientation showed the opposite effect. Moreover, cell-cycle analysis demonstrated that the G1-phase was shortened in the cells expressing the sense construct. Before studying how ProTalpha affects differentiation, we showed that the down-regulation of ProTalpha gene during differentiation occurs in all mammalian cell lines (HL-60, K562, U937, MEL C88, N2A and PC12) analysed. The biological effect evoked by the induction of the ProTalpha sense vector was the retardation of cell differentiation, although expression of the antisense construct showed no effect on differentiation. In conclusion, our findings provide evidence that ProTalpha is directly implicated in cellular proliferation and that the maintenance of high levels of ProTalpha inside HL-60 cells is incompatible with their ability to differentiate.

Chinese hamster ovary (CHO) cells are the system of choice for the production of complex molecules, such as monoclonal antibodies. Despite significant progress in improving the yield from these cells, the process to the selection, identification, and maintenance of high-producing cell lines remains cumbersome, time consuming, and often of uncertain outcome. Matrix attachment regions (MARs) are DNA sequences that help generate and maintain an open chromatin domain that is favourable to transcription and may also facilitate the integration of several copies of the transgene. By incorporating MARs into expression vectors, an increase in the proportion of high-producer cells as well as an increase in protein production are seen, thereby reducing the number of clones to be screened and time to production by as much as 9 months. In this chapter, we describe how MARs can be used to increase transgene expression and provide protocols for the transfection of CHO cells in suspension and detection of high-producing antibody cell clones.

The artiele describes the development of a eblíd w¡th Joubert Syndrume who, sinee Ihe age of 16 months, has received personalized stimulation therapy at borne and in Ihe Early Intervention Unu (ElE) of thc Faculty, in each of the five arcas considered by the Portage (juide (o Early Educarion: socíalization, language. seiI-heip, cognition, and rnororicity.Repeated evaLuarions durino the treatment (t'p lo age 40 months) showed sLow progress ti oil developrnental arcas, as well os o genes-al attitude to and capacity for [earning.During treatmenr. greatest progress was made in Ihe arcas of cognition and comniunication. Kev~vonls: Joul,ert svndrcnne, vermis agenesia, ccclv intercention Este artículo describe el desarrollo de un niño con síndrome do ,Joubert, atendido en la Unidad de Atención Temprana de una Facultad de Psicologia. El sujeto se incorporó a la edad de 16 meses a un programa individualizado de estimulación temprana en cada una de las cinco áreas consideradas por la Guia Portage de Atención Temprana: socialización, lenguaje, auto-ayuda, cognición y motricidad. El programa se puso en práctica tanto en la unidad como en el hogar tas evaluaciones realizadas a lo largo del periodo de tratamiento

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