Abstract: Provided herein are genetically engineered gas vesicle expression systems (GVES) that are configured to express gas vesicles (GVs) in a mammalian cell, related gas vesicle polynucleotide constructs, gas vesicle reporting genetic circuits, vectors, genetically engineered mammalian cells, non-human mammalian hosts, compositions, methods and systems, which in several embodiments can be used together with contrast-enhanced imaging techniques to detect and report biological events in an imaging target site comprising a mammalian cell and/or organism.

Abstract: Provided herein are genetically engineered gas vesicle expression systems (GVES) that are configured to express gas vesicles (GVs) in a mammalian cell, related gas vesicle polynucleotide constructs, gas vesicle reporting genetic circuits, vectors, genetically engineered mammalian cells, non-human mammalian hosts, compositions, methods and systems, which in several embodiments can be used together with contrast-enhanced imaging techniques to detect and report biological events in an imaging target site comprising a mammalian cell and/or organism.

Abstract: Disclosed herein include methods, compositions, and kits suitable for use in dynamic non-destructive imaging. The non-destructive imaging can be nonlinear ultrasound imaging. There are provided, in some embodiments, nucleic acid compositions encoding gas vesicles (GVs) capable of producing nonlinear ultrasound contrast upon expression in a prokaryotic cell (e.g., a probiotic bacterial cell) or a eukaryotic cell (e.g., a therapeutic mammalian cell).

Abstract: Provided herein are genetically engineered gas vesicle expression systems (GVES) that are configured to express gas vesicles (GVs) in a mammalian cell, related gas vesicle polynucleotide constructs, gas vesicle reporting genetic circuits, vectors, genetically engineered mammalian cells, non-human mammalian hosts, compositions, methods and systems, which in several embodiments can be used together with contrast-enhanced imaging techniques to detect and report biological events in an imaging target site comprising a mammalian cell and/or organism.

Abstract: Disclosed herein include methods, compositions, and kits enabling expression of multiple proteins from a single mRNA with a predetermined stoichiometry. There are provided, in some embodiments, nucleic acid compositions comprising a promoter operably linked to a polynucleotide comprising a first nucleic acid unit encoding first unit payload protein(s) and a second nucleic acid unit encoding second unit payload protein(s). The first nucleic acid unit and the second nucleic acid unit can each comprise a 3? engineered translation initiation site (eTIS) comprising a three-nucleotide tunable element immediately upstream of a start codon. The eTIS of each of the first nucleic acid unit and the second nucleic acid unit can be configured to achieve a predetermined stoichiometry of the first unit payload protein(s) and the second unit payload protein(s) in a cell or cell-like environment.