Humanized rodents that express heavy chain containing vl domains

A mouse whose germline genome comprises:

• (a) an insertion of one or more unrearranged human VL gene segments and one or more unrearranged human JL gene segments upstream of an endogenous mouse light chain constant region sequence, wherein the one or more unrearranged human VL gene segments and one or more unrearranged human JL gene segments are operably linked to the endogenous mouse light chain constant region sequence,
• (b) an insertion of one or more unrearranged human VL gene segments and one or more unrearranged human JL gene segments upstream of an endogenous mouse heavy chain constant region sequence, wherein the one or more unrearranged human VL gene segments and one or more unrearranged human JL gene segments are operably linked to the endogenous mouse heavy chain constant region sequence, and
• (c) an inserted nucleic acid sequence that encodes a mouse ADAM6 protein, wherein the mouse ADAM6 protein is expressed from the inserted nucleic acid sequence, and wherein the nucleic acid sequence that encodes the mouse ADAM6 protein is present in the germline genome of the mouse at a position adjacent to a mouse immunoglobulin-containing and cysteine-rich receptor 1 (IGCR1),
• wherein B cells of the mouse express antibodies that each include two immunoglobulin light chains paired with two immunoglobulin heavy chains, wherein each light chain comprises a human light chain variable domain operably linked to a mouse light chain constant domain and each heavy chain comprises a human light chain variable domain operably linked to a mouse heavy chain constant domain.

A method comprising:

• (a) immunizing a mouse with an antigen of interest, wherein the germline genome of the mouse comprises:
• (i) an insertion of one or more unrearranged human VL gene segments and one or more unrearranged human JL gene segments upstream of an endogenous mouse light chain constant region sequence, wherein the one or more unrearranged human VL gene segments and one or more unrearranged human JL gene segments are operably linked to the endogenous mouse light chain constant region sequence,
• (ii) an insertion of one or more unrearranged human VL gene segments and one or more unrearranged human JL gene segments upstream of an endogenous mouse heavy chain constant region sequence, wherein the one or more unrearranged human VL gene segments and one or more unrearranged human JL gene segments are operably linked to the endogenous mouse heavy chain constant region sequence, and
• (iii) an inserted nucleic acid sequence that encodes a mouse ADAM6 protein, wherein the mouse ADAM6 protein is expressed from the inserted nucleic acid sequence,
• wherein B cells of the mouse express antibodies that each include two immunoglobulin light chains paired with two immunoglobulin heavy chains, wherein each light chain comprises a human light chain variable domain operably linked to a mouse light chain constant domain and each heavy chain comprises a human light chain variable domain operably linked to a mouse heavy chain constant domain, and
• (b) isolating:
• (i) an antibody that binds the antigen of interest;
• and/or
• (ii) one or more B lymphocytes of the mouse, wherein the one or more B lymphocytes express an antibody that binds the antigen of interest.

A method comprising:

• (a) immunizing a mouse with an antigen of interest, wherein the germline genome of the mouse comprises:
• (i) an insertion of one or more unrearranged human VL gene segments and one or more unrearranged human JL gene segments upstream of an endogenous mouse light chain constant region sequence, wherein the one or more unrearranged human VL gene segments and one or more unrearranged human JL gene segments are operably linked to the endogenous mouse light chain constant region sequence,
• (ii) an insertion of one or more unrearranged human VL gene segments and one or more unrearranged human JL gene segments upstream of an endogenous mouse heavy chain constant region sequence, wherein the one or more unrearranged human VL gene segments and one or more unrearranged human JL gene segments are operably linked to the endogenous mouse heavy chain constant region sequence, and
• (iii) an inserted nucleic acid sequence that encodes a mouse ADAM6 protein, wherein the mouse ADAM6 protein is expressed from the inserted nucleic acid sequence, and wherein the nucleic acid sequence that encodes the mouse ADAM6 protein is present in the germline genome of the mouse at a position adjacent to a mouse immunoglobulin-containing and cysteine-rich receptor 1 (IGCR1),
• wherein B cells of the mouse express antibodies that each include two immunoglobulin light chains paired with two immunoglobulin heavy chains, wherein each light chain comprises a human light chain variable domain operably linked to a mouse light chain constant domain and each heavy chain comprises a human light chain variable domain operably linked to a mouse heavy chain constant domain, and
• (b) isolating:
• (i) an antibody that binds the antigen of interest;
• and/or
• (ii) one or more B lymphocytes of the mouse, wherein the one or more B lymphocytes express an antibody that binds the antigen of interest.