Humanized non-human animals with restricted immunoglobulin heavy chain loci

A male mouse comprising an insertion including an unrearranged human genomic sequence including a single human VH gene segment operably linked to at least one human DH gene segment, and at least one human JH gene segment, wherein the single human VH gene segment, the at least one human DH gene segment, and the at least one JH gene segment are operably linked to a mouse immunoglobulin constant region gene at the endogenous immunoglobulin heavy chain locus, wherein the single human VH gene segment is VH1-69 or a polymorphic variant thereof, wherein the insertion disrupts the function of an endogenous ADAM6 protein, and wherein the disruption of the endogenous ADAM6 function is associated with a reduction in fertility in male mice;

• and wherein the mouse comprises a mouse ADAM6 sequence located between the single human VH gene segment and the 5′ most DH gene segment, wherein the mouse ADAM6 sequence encodes a mouse ADAM6 protein that is functional in a male mouse, wherein the functional mouse ADAM6 protein is expressed and the male mouse has wild-type fertility.

A method for modifying an immunoglobulin heavy chain locus of a mouse, comprising:

• (a) making a first modification of the mouse immunoglobulin heavy chain locus, wherein the first modification comprises an insertion of one or more unrearranged human immunoglobulin gene sequences at the mouse immunoglobulin heavy chain locus, including a single human VH gene segment, one or more DH gene segments, and one or more JH gene segments, wherein the single human VH gene segment, one or more DH gene segments, and one or more JH gene segments are operably linked with a mouse immunoglobulin constant region gene at the endogenous immunoglobulin heavy chain locus, wherein the single human VH gene segment is VH1-69 or a polymorphic variant thereof, wherein the insertion disrupts the function of an endogenous ADAM6 protein, and wherein the disruption of the endogenous ADAM6 function is associated with a reduction in fertility in male mice;
• and
• (b) making a second modification of the mouse which comprises an insertion of a mouse ADAM6 sequence between the single human VH gene segment and the 5′ most DH gene segment, wherein the mouse ADAM6 sequence encodes a mouse ADAM6 protein that is functional in a male mouse, wherein the functional mouse ADAM6 protein is expressed and the male mouse has wild-type fertility.